In Salesforce, a permission set is a collection of permissions and settings that give users access to certain features and functions. These permission sets can be assigned to users to grant them specific access and permissions, without changing their profile or role.
Here's an example:
Let's say you have a Salesforce org with several profiles for different user groups, such as a Standard User profile for sales reps and a System Administrator profile for system admins. You have a sales rep who needs access to a new feature that is not available in their Standard User profile, but you don't want to change their profile because it would give them access to other areas of the org that they don't need.
In this case, you can create a permission set that includes the permissions for the new feature and assign it to the sales rep. This will give them access to the new feature without changing their profile or giving them access to any other unnecessary areas of the org.
Permission sets are different from profiles in that they are more flexible and granular. While profiles apply to an entire user group and cannot be customized for individual users, permission sets can be customized and assigned to specific users to grant them access to only the features and functions they need. This allows you to grant users access to specific features and functions without changing their profile or role, which can be useful if you have users with diverse needs or if you want to grant temporary access to specific features. Hope this Helps !