Simply you log in then put you a password and you logged in Gmail.com.
Your searches and browsing activity are saved in your web when it is turned on and you are signed in to your Google account.
This gives you better result and recommendation actress Google’s products.
HOW WEB& APP ACTIVITIES WORKS -
Search and ad may be customized using search related activity from your device even if you are signed out.
That why I approach to Gmail.com.