In Lightning Experience, each user’s Top Results page includes the objects they use the most.

For new users or users that have little to no activity in Salesforce for over 90 days:
– Default global search in Classic returns all objects (same results as clicking ‘Search All’).
– Default ‘Top Results’ in Lightning returns the objects that are set in the current Lightning App’s navigation menu.

New User Search:

Searches only the Tabs from the App.

Old User Search:

Searches other objects too where they work the most other than the objects tabs from the App.