Unfortunately too much. 

Say you are asked by a stranger on a two story elevator ride-

“Kind sir/madam can you explain the difference between an interior architect and an interior designer?”

OK I am sure that happens a lot so here is my response;

An interior architect designs interior space to suit the building.  

An interior designer designs interior space to suit the user.

(actually the reality for both is somewhere in the middle but just go with me here)

So with that PROFESSIONALINTERIORDESIGNER has clarified our mighty identity crisis. We are spatial and we design interior space to suit the user. Elevator ride over. Carry on.