Organization-Wide Permission Sets in Salesforce

Organization-wide permission sets are not associated with a specific user license. You can create a single permission set and assign it to users with different user licenses.

While creating a Permission Set, it asks for User license and it can be associated to that license users.

But Organization-wide permission sets are not associated with a specific user license. So, it can be assigned to any user with any license.

 To create this go to Setup --> Manage Users --> Permission Sets.