Can these chess terms be used interchangeably? I am confused by the usage of the following chess terms: 'positional advantage', 'initiative', 'attack', 'pressure', 'aggressive/active moves' and 'play/counterplay'. Do they mean the same thing? Can they be used interchangeably?
"positional advantage"  -- This could refer to a better pawn structure or deployment of forces; a knight outpost or the opponent has doubled pawns etc.
In battle it could be having the high-ground.

"initiative" and "attack" are used similarly, but "initiative" is who can make the next threat.  For example, in Tennis: you have the serve = initiative.  You make a good serve and are able to rush the net (keeping the initiative -- threat after threat) = attack.

"pressure" is making threats against weaknesses.  So, you might have a positional advantage, say your opponent has weak pawns, but if you don't attack them where is the pressure?

"play" and "counter play" refer to the ability to make threats.  If you are completely on the defensive then you have no play.

"active moves" are moves that seek to attack/counter-attack as opposed to passivity.

So now I hope you can understand this: 
"I had a positional advantage, which I turned into an attack, but he sacrificed the exchange and got counter-play.  I defended and was able to consolidate my material advantage."