It is used when addressing more than one person and is equivalent to "you have" in English.
Here are some examples of how "avez" is used:
* Vous avez un chien. (You have a dog.)
* Avez-vous faim? (Are you hungry?)
* Ils vous ont dit que vous avez raison. (They told you that you are right.)
Let me know if you'd like more examples or have any other questions about French grammar!