What is Profile in Salesforce?

Profile is a collection of Settings and Permissions which determines

1. What users can see on the UI

2. What functionality users can access

3. What records users can view, edit and delete

Settings determine what users can see, for example, apps, tabs, fields, and record types. Permissions determine what users can do, for example, create or edit records of a certain type, run reports, and customize the app.