A Modalverb or modal auxiliary verb is a special class of verbs that is usually combined with another verb (Vollverb). The Modalverb will add an additional dimension to the meaning of the Vollverb. The Modalverb "können" means "to be able to". In the following example, you will see how the Modalverb adds to the meaning of the Vollverb "sprechen".

Beispiel:
- Er spricht Deutsch und Englisch. (He speaks German and English)
- Er kann Deutsch und Englisch sprechen. (He is able to speak German and English)

Note the positions of the Modalverb and Vollverb in the sentence. The Modalverb is conjugated and occupies the second position in the sentence, while the Vollverb is in infinitive at the end of the sentence. 

Struktur:
.... [Position 2: konjugiertes Modalverb] .............................. [Satzende: Vollverb im Infinitiv]