Last month Google has made its video conferencing service Google Meet for free to use. And now Google Meet coming in Gmail mobile app. Google Meet now integrates the dedicated Meet tab in the Gmail app in the coming weeks. This means users can easily join the meeting with a simple tap.
To getting started with Google Meet, just tap on the “New Meeting” button to start the meeting, and get a sharable link, or schedule meeting in the calendar. You can join the meeting by taping on the “Join with a code” by entering the meeting code.
If you don’t want this feature to appear in the Gmail app tab, click on the setting in the Gmail app from the hamburger menu in the top left corner, now tap on your account and uncheck the Meet, the Meet tab now hide for Gmail mobile app.

Note: If you click on a link in the Meet app, you will still stay in Meet and not be redirected to the Gmail app. These changes will roll out over the next few weeks.
Read more from Google Support page