The IUPAC nomenclature of inorganic chemistry is a systematic method of naming inorganic chemical compounds as recommended by the International Union of Pure and Applied Chemistry (IUPAC). Ideally, every inorganic compound should have a name from which an unambiguous formula can be determined. There is also an IUPAC nomenclature of organic chemistry.
The names "caffeine" and "3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione" both describe the same chemical. The systematic name encodes the structure and composition of the caffeine molecule in some detail, and provides an unambiguous reference to this compound, whereas the name "caffeine" just names it. These advantages make the systematic name far superior to the common name when absolute clarity and precision are required. However, even professional chemists will use the non-systematic name almost all of the time, because caffeine is a well-known common chemical with a unique structure. Similarly, H₂O is most often simply called water in English, though other chemical names do exist.
Positively charged ions are called cations and negatively charged ions are called anions. The cation is always named first. Ions can be metals or polyatomic ions. Therefore the name of the metal or positive polyatomic ion is followed by the name of the non-metal or negative polyatomic ion. The positive ion retains its element name whereas for a single non-metal anion the ending is changed to -ide.
Example: sodium chloride, potassium oxide, or calcium carbonate.
When the metal has more than one possible ionic charge or oxidation number the name becomes ambiguous. In these cases the oxidation number of the metal ion is represented by a Roman numeral in parentheses immediately following the metal ion name. For example in uranium(VI) fluoride the oxidation number of uranium is 6. Another example is the iron oxides. FeO is iron(II) oxide and Fe₂O₃ is iron(III) oxide.
An older system used prefixes and suffixes to indicate the oxidation number, according to the following scheme:
Thus the four oxyacids of chlorine are called hypochlorous acid (HOCl), chlorous acid (HOClO), chloric acid (HOClO₂) and perchloric acid (HOClO₃), and their respective conjugate bases are the hypochlorite, chlorite, chlorate and perchlorate ions. This system has partially fallen out of use, but survives in the common names of many chemical compounds: the modern literature contains few references to "ferric chloride" (instead calling it "iron(III) chloride"), but names like "potassium permanganate" (instead of "potassium manganate(VII)") and "sulfuric acid" abound.

Single atom anions are named with an -ide suffix: for example, H,
The prefix bi- is a deprecated way of indicating the presence of a single hydrogen ion, as in "sodium bicarbonate" (NaHCO₃). The modern method specifically names the hydrogen atom. Thus, NaHCO₃ would be pronounced "sodium hydrogen carbonate". Traditional naming
An ionic compound is named by its cation followed by its anion. See polyatomic ions for a list of possible ions.
For cations that take on multiple charges, the charge is written using Roman numerals in parentheses immediately following the element name) For example, Cu(NO₃)₂ is copper(II) nitrate, because the charge of two nitrate ions (NO₃) is 2 × −1 = −2, and since the net charge of the ionic compound must be zero, the Cu ion has a 2+ charge. This compound is therefore copper(II) nitrate. In the case of cations with a 4+ oxidation state, the acceptable format for the Roman numeral 4 is IV and not IIII.
The Roman numerals in fact show the oxidation number, but in simple ionic compounds (i.e., not metal complexes) this will always equal the ionic charge on the metal. For a simple overview see [1], for more details see selected pages from IUPAC rules for naming inorganic compounds.

Naming simple ionic compounds
Monatomic anions:
Cl permanganate

Naming hydrates
Inorganic molecular compounds are named with a prefix (see list above) before each element. The more electronegative element is written last and with an -ide suffix. For example, CO₂ is carbon dioxide. Although CCl₄ is sometimes called carbon tetrachloride under this rule, it is not an inorganic molecule and is more properly called tetrachloromethane. There are some exceptions to the rule, however. The prefix mono- is not used with the first element; for example, CO₂ is carbon dioxide, not "monocarbon dioxide". Sometimes prefixes are shortened when the ending vowel of the prefix "conflicts" with a starting vowel in the compound. This makes the compound easier to speak; for example, CO is "carbon monoxide" (as opposed to "monooxide").

Naming molecular compounds
Acids are named by the anion they form when dissolved in water. If an acid forms an anion named ___ide, it is named hydro___ic acid. For example, hydrochloric acid forms a chloride anion. Secondly, anions with an -ate suffix are formed when acids with an -ic suffix are dissolved, e.g. chloric acid (HClO₃) dissociates into chlorate anions to form salts such as sodium chlorate (NaClO₃); anions with an -ite suffix are formed when acids with an -ous suffix are dissolved in water, e.g. chlorous acid (HClO₂) disassociates into chlorite anions to form salts such as sodium chlorite (NaClO₂).

Naming acids
With the last revision of the nomenclature, many things changed. Most important is, that there is no absolute right name for one compound anymore. As long as the name describes the compound sufficiently and unambiguously, the name is correct. Old names such as water, carbonyl or cyano are still tolerated. — The "old names" may still have to be understood, but the systematic IUPAC nomenclature is easier to learn (because it is systematic) and always right to use.
There are basically two different ways to describe a compound: compositional and substitutive nomenclature.

2005 revision of IUPAC's nomenclature for inorganic compounds
This ansatz tries to describe how a molecule is constructed from some kind of core, in partial imitation of the system for naming coordination compounds. The core(s) of the molecule is taken to be the atom with the lowest electronegativity (EN) (e.g. in CO, C, with EN=2.5, is taken to be the core, whereas O has EN=3.5). The choice of core element determines the stem name of the compound. If the compound is negatively charged, the name is augmented by a suffix: -ide if no other element is present and -ate otherwise.
Then the surrounding atoms and groups are described in the manner used to describe the ligand portions of coordination compounds. The ligand names are determined similarly to the core name. The suffix -o marks a group as a ligand. Identical groups are named collectively using a counting prefix (i.e. tri-, tetra- or bis-).
After the naming of atoms, designators for charge, radical function, water of crystallization, bridging or multicoordinating ligands are added. Brackets are employed to eliminate ambiguities. Last but not least, the ligand names (if there are distinct ligands) are listed separately in alphabetical order; the alphabetical naming order disregards the counting prefixes.
Cations and anions are treated separately (in that order).
Exemplification:

Substitutive nomenclature

IUPAC nomenclature
IUPAC nomenclature of organic chemistry
List of inorganic compounds
Water of Crystallization