Security roles define sets of access rights that can be then inherited by individual users. For example you can define the role "Data entry" and give that role access to certain tools.
Giving a user the role "Data entry":
For everything marked as "(undefined)" you're expressing no opinion as to the rights this user should have: that means that the user may get rights from the default user or other roles. In this example, though, no matter what rights the person may get from the default user or other roles before this one they will not have access to "Enter account records for multiple people at once" unless they're given that right explicitly or via a role which comes after this one.
The Copy compatibility mode rights link, if visible, can be used to copy the compatibility mode rights from any other user to this role.