Google has released an updated UI for Gmail in February. The new look brings Meet, Chat and Spaces and applies more of Material You style effects.
From now on, the new look will be released for everyone. So your account will change to the new UI very soon.
It's not a huge change, but Google seems to be trying to bring the look of the suite workspace her to everyone. Of course, it does this to make Office more competitive.
According to Google, you can choose which ones applications they will be included in the menu from Quick settings, from where you can go back to the old look if you prefer.
Google also says it may take more than a few weeks to get the new UI into your personal Gmail accounts.
