Imagine asking a friend to come over, telling a group of friends to wait, or asking a shop assistant for help. In all these situations you need the imperative — the form German uses to tell someone to do something directly, without a question, just a straightforward instruction or request.
German changes the verb depending on who you're talking to, but the deciding factor isn't gender or number — it's your relationship to the person and which pronoun you'd normally use for them. One friend you'd call du? A group of friends you'd call ihr? Someone you address more formally with Sie? The three imperative forms map exactly onto these pronouns you already know.
Building the imperative is straightforward once you know the steps. Start from the present-tense verb form for that pronoun, then drop the pronoun itself. With du, also drop the ending -st: du kommst becomes Komm!. With ihr, keep the ending as is: ihr kommt becomes Kommt!. With Sie, keep the verb exactly as it appears with Sie, but move Sie after the verb instead of before it: Sie kommen becomes Kommen Sie!. Verbs that change their stem vowel in the present tense (sprechen → du sprichst) keep that change only in the du form — Sprich! — while ihr and Sie stay unchanged.
A point worth remembering: with du and ihr, the pronoun disappears completely — you say Komm! and Kommt!, never a stated pronoun before the verb. With Sie, though, the pronoun can never be dropped: it must stay right after the verb, because the verb form alone (kommen) doesn't tell the listener who is being addressed.
A common mistake is leaving du in front of the verb as in a normal statement (Du kommst!) instead of dropping it and adjusting the verb (Komm!), or forgetting to invert the word order in the Sie form and saying Sie kommen! instead of the correct Kommen Sie!.