Configuring user permissions with profiles and permission sets
We've seen that a user is related to a specific license type, and in the same way, each profile is related to a specific license type. This means that when you select a license type when defining a user, only a subset of all the available profiles is allowed.
This is what you see in your org when clicking on Setup | Users | Profiles:
As you can see, we have standard and custom profiles. Standard profiles come built into your org and their permissions are roughly unchangeable, which is why you should always clone a profile to create a new custom one with the desired permissions.
Remember that you cannot change a profile's license type.
Further reading
If you want to look deeper into profile permissions, jump to Salesforce Help at https://help.salesforce.com/articleView?id=admin_userprofiles.htm&type=5.
As we...