Interpretation

is how we interpret. For example, my interpretation of the following constants (nullary function symbols) is:

treeIF = tree in real world

catIF = cat in real world

Yep, I do notice, the domain being used is our real world (a free domain that you always use, in fact).

PS: In this case, IF (Interpretation of Fadirra) is my interpretation. You have your own interpretation, don't steal mine!