Definition - Verbs are words that describe a state of being or an action. Examples of German verbs are:
             • sein [to be], haben [to have], gehen [to go], tun [to do], hören [to hear], kaufen [to buy], ...

Types - There are several kinds of verbs. The following definitions refer to the most used terms in grammatical explanations.

Infinite verbs only name the state of being or action, without giving other information.
             • Du siehst mich die blaue Tasche tragen. [You see me carry/carrying the blue bag.]
             • Es ist gesund Obst zu essen. [It is healthy to eat fruit.]
             • Wir möchten Kaffee trinken. [We would like to drink coffee.]

Infinite verbs can be conjugated into finite forms. Finite verbs not only name the state of being or action, but also indicate who performs the action (the subject) and when the action is performed (e.g. present, past, future).
             • Ich trage die blaue Tasche. [I carry the blue bag.]
             • Karl hat ein gelbes Auto. [Karl has a yellow car.]
             • Wir trinken den Kaffee. [We drink the coffee.]
             • Gestern kauften Sie ein Buch. [Yesterday you bought a book.]
             • Morgen werden sie ins Kino gehen. [Tomorrow they will go to the cinema.]

Transitive verbs name actions that 'aim' at an object, either a thing or a person. These verbs need an object to be complete and make sense. Verbs like 'bringen [to bring]' or 'tragen [to wear]', for instance, do not make sense unless we know what is being brought or what is being worn.
             • Der Briefträger bringt die Post. [The postman brings the mail.]
             • Der Mann und die Frau nehmen das Taxi. [The man and the woman take the taxi.]
             • Elke trägt ein blaues Kleid. [Elke wears a blue dress.]

Intransitive verbs do not 'aim' at anything or anybody. Verbs like 'laufen [to run]' or 'fliegen [to fly]' describe actions that do not have an impact on an object.
             • Hans geht. [Hans walks.]
             • Das graue Flugzeug fliegt. [This gray plane is flying.]

Note: some verbs can be both transitive and intransitive.
             • Ich fliege dieses graue Flugzeug. [I fly this gray plane.]
             • Karl fährt ein gelbes Auto. [Karl drives a yellow car.]

Conjugation - Regular verbs conjugate into the various finite forms according to a fixed pattern. If we know the infinite form of a regular verb, we can conjugate the verb following this regular pattern. In German this means that we delete a certain ending from the infinite form and replace it with other endings.

An example of German regular verb:
             • Infinite - machen [to make]
             • Conjugation - ich mache [I make]
                                    - du machst [you make]
                                    - er/sie/es macht [he/she/it makes]
                                    - wir machen [we make]
                                    - ihr macht [you make]
                                    - sie machen [they make]
                                    - Sie machen [you make - polite form]

Irregular verbs, on the contrary, do not follow a regular model.

An example of German irregular verb:
             • Infinite - essen [to eat]
             • Conjugation - ich esse [I eat]
                                    - du isst [you eat]
                                    - er/sie/es isst [he/she/it eats]
                                    - wir essen [we eat]
                                    - ihr esst [you eat]
                                    - sie essen [they eat]
                                    - Sie essen [you eat - polite form]