HI,
A permission set is a collection of settings and permissions that give users access to various tools and functions. The settings and permissions in permission sets are also found in profiles, but permission sets extend users’ functional access without changing their profiles.
Users can have only one profile but, depending on the Salesforce edition, they can have multiple permission sets. You can assign permission sets to various types of users, regardless of their profiles.
Create permission sets to grant access among logical groupings of users, regardless of their primary job function. For example, let’s say you have several users with a profile called Sales User. This profile allows assignees to read, create, and edit leads. Some, but not all, of these users also need to delete and transfer leads. Instead of creating another profile, create a permission set.