De leraar legt de les uit.
English: The teacher explains the lesson.
The 'bedrijvende vorm' in Dutch is the active voice. In the active voice, the subject of the sentence does the action.
Use the active voice in Dutch when you want to clearly show who is doing the action. It is the most common way to build sentences in Dutch.
De leraar legt de les uit.
English: The teacher explains the lesson.
Zij schrijft een brief.
English: She writes a letter.
Wij eten pizza.
English: We eat pizza.
Jullie maken huiswerk.
English: You (plural) do homework.
De kat vangt de muis.
English: The cat catches the mouse.