The @mentions feature for GPTs, which is now live for all paid ChatGPT users (Plus, Team, Enterprise), allows you to type "@" in a conversation to activate an inline selector that shows your pinned and recent GPTs. You can select a GPT to direct your next message, while retaining the context of the current conversation. This allows users to bring GPTs with different capabilities, styles, instructions, etc. into the same shared conversation to streamline your chats.
For Enterprise users, some GPTs may be grayed out when they cannot be used to your workspace restrictions set by your workspace Owner.