The attribute type editor is the one-stop shop where you can define all aspects of your attribute type.
The Overview page is where the user can edit the properties of the attribute type.
User can edit:
The Source code page is where the user can see the result of his actions in the Overview page and what source code will be generated in the schema file.
The Used By page is where the user can see in which object class(es) is used this attribute type (as mandatory or optional attribute type).