Ehmm
What does "explore the pin" mean?

It probably said to "exploit" the pin, by adding pressure.
That was my 1st thought too.

I think somebody is confused; the usual terminology is "exploit the pin." Exploit meaning "to take advantage of" or "to make use of".
It usually means moving a piece to a square that would not be safe if the enemy piece that guards that square was not pinned.
For example after 1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. d4 ed4 5. 0-0 Ne4 6. Re1 d5 7. Bd5 Qd5 and now white can exploit the pin on the d-pawn and the pin on the knight to play Nc3 winning back the sacrificed piece.
Hey all,
I've been reading some chess literature lately and in a lot of game analysis it says something like: "Black moves his knight to e4 in order to explore the pin". I know what a pinned piece is, but don't know in which way I should interpret the 'exploring' of a pin.
In most cases this pinned piece is still protected by a pawn. Why explore it by bringing in another piece if taking the pinned piece just results in a retake with the pawn? This would make the "exploration" just a piece exchange with as only positive side the result of a weaker pawn structure for your opponent.
Can anyone give some examples of truly useful tactics/strategies in these kind of situations?
Thanks,
Jan