Custom data is used to add new fields to the database so that it meets the needs of your organization. It may be a text field, text area, checkboxes, yes/no, etc.
To add new fields, go to Administer >> Customize >> Custom data
Here you can create new data groups and then add custom fields to those groups. Once you have created the custom data fields, you will be able to use those inside profiles.
Adding and editing fields is very easy. Just choose the appropriate option - add a field or customize one already there - and then follow the options down the screen.
You can read more about custom data here and here.
Once you have added a custom field to a profile, editing the name inside custom data will not change it on the profile listing. You will need to go to the appropriate profile, edit the field, and reselect it from the drop down so that it picks up the new name.
