Definition - Nouns are 'names' we use to identify people, things, places, or ideas.
Examples of German nouns are:
             • Peter [Peter], Koffer [suitcase], Firma [company], Buch [book], Österreich [Austria], Dank [thank-you], ...

Note: in German all nouns are written with an initial capital letter.

Types - Nouns can be of many different types.

Proper nouns are names of specific people, things, locations, or ideas:
             • Karl [Karl], die Vereinten Nationen [the United Nations], Wien [Vienna], Kommunismus [Communism], ...

Common nouns are names of general 'categories' of people, objects, places, or concepts:
             • Junge [boy], Organisation [organisation], Stadt [town], Schönheit [beauty], ...

Countable nouns are names of anything that can be counted:
             • ein Koffer [one suitcase], drei Bücher [three books], vielen Dank [many thanks], ...

Uncountable nouns name what cannot be counted:
             • Wein [wine], Luft [air], Wasser [water], ...

Note: some nouns can be used as countable or uncountable depending on what we want to say.
Examples of uncountable nouns:
             • Deutsches Bier ist gut. [German beer is good.]
             • Das ist Kaffee. [This is coffee.]
Examples of uncountable nouns used with a 'countable meaning':
             • Vier Bier kosten zwei Euro. [Four beers -- glasses/cans/bottles/... of beer -- cost two Euros.]
             • Ich trinke einen Kaffee. [I drink a coffee -- cup of coffee.]

Collective nouns refer to a group made up of more than one person or thing:
             • Leute [people], Familie [family], Obst [fruit], Herde [herd], ...

Gender - Some languages divide nouns according to gender. In German there are three genders: masculine, feminine, and neuter.
This concept is not easy to understand for speakers of languages that do not have genders, especially because the genders of nouns do not follow a clear logic. Some nouns that name masculine people or things are masculine, but others are feminine or neuters. Trying to 'reason' about the gender of a noun is not very helpful. The best is to simply learn the gender of the nouns by learning other words that indicate gender, for instance the articles.

Examples of German nouns divided by gender:
             • Masculine - der Koffer [the suitcase], der Dank [the thank-you], der Wein [the wine]
             • Feminine - die Briefmarke [the stamp], die Schönheit [the beauty], die Luft [the air]
             • Neuter - das Buch [the book], das Land [the country], das Wasser [the water], das Obst [the fruit]

Number - Most nouns have a singular and a plural form. Singular refers to one (only one person, thing, or 'group'), while plural refers to more than one.

Examples of singular and plural form:
             • Singular - ein Junge [one boy], eine Firma [a company], ein Land [a country]
             • Plural - zwei Jungen [two boys], hundert Firmen [hundred companies], viele Länder [many countries]