Here you can name Custom Fields for Projects.
Custom Fields can be used to store additional information for a project. They can also be used on Custom Reports, or could be used to pull text into your Project Number Format.
There are 30 customizable fields available to you: fourteen Text fields (two of which are long text fields), four Number fields, four Date fields, four Yes/No (Boolean), and four List fields where you can customize a drop-down list. Short text fields have a limit of 300 characters, long text fields have a limit of 1000 characters.
When you click the Manage link next to a field, the following dialog will open that allows you to add/edit/delete items to the list. You can also use the Move Up/Down buttons to choose the order of the items in the list.