Selection Category :
 here you can choose whether you want to work with VEF (Vert, Edge, or Face) or Object selection sets 

Save Selection :
Depending on whether you have your category set to VEF or Object, it will save the selection in a list with a custom icon so you you're able to easily recognize the selection type.

Selections List :
Here you're able to choose your selection and use it by clicking on the icon. 
Edit the name of your selection by double clicking on the name and assigning a new name to it.
Update your selection with the refresh icon.
Delete your selection with the cross/delete icon.

Quick note. for the object selection sets you're able to select multiple objects as a set which can be very helpful.