There is a wide variety of Emotes to allow for quick responses while communicating with other users. Additionally, there are Emotes called "Sync Emotes", that can be performed together by multiple avatars.
When approaching an avatar performing an Emote, a sync button will appear, which will allow you to perform the same Emote at the same time. You can also start your own by opening the Emote list and selecting a Sync Emote, which are marked with a circle in the background.