1.
If one thing is added on to another, it is attached to the other thing, or is made a part of it.
Holidaymakers can also add on a week in Majorca before or after the cruise...
To the rear is a large dining room–added on early this century.
PHRASAL VERB : usu passive , V P n , V-ed P
2.
If you add on an extra amount or item to a list or total, you include it.
Many loan application forms automatically add on insurance.
PHRASAL VERB : V P n (not pron) , also V n P