Lookups are the name given to all editable sets of dropdown menus available in your Senta workspace. There are many pre-loaded in Senta, but all can be changed to display the options you want, or you can add your own.
You'll probably end up using Lookups in tasks: When you select a drop down task type, you'll need to assign a Lookup at this point.
You can find Lookups in the Settings Menu:
Here you'll find the default list of Lookups. Let's take 'Client Type' as an example:
Within the Lookup editor, you can change names of existing items in the Lookup:
Or you could add new items, such as an additional Contact type:
You can also change the order that items appear in the Lookup by using the arrows on the right hand side.