Block Recovery?

I'm not a pro, but also not a newbie in PoE... But I still don't really get what does Block Recovery do. There's a chance to block an enemy attack, and if I block successfully my block is recovering, and that Block Recovery +XX(X)% decreases the time of the recovery? Am I right?

Not just your block is recovering. Your character as a whole suffers a block animation that renders them incapable of performing any actions while they're recovering. So decreasing that time is always good, especially in the event of multiple blocks in a row.

I've heard it's possible to become 'stun locked' by blocking and then blocking again while you're still recovering from the first block.

Its like getting stunned from getting hit, without taking the damage.

I found this post old, but here is the answer :

Block recovery decrease time between block when the animation of block trigger.
The block animation trigger if you would have been stun by the blocked hit.

Source :
http://pathofexile.gamepedia.com/Blocking

"

When an attack is blocked, the game first calculates if the attack would have caused a stun were it not blocked. If it would have caused a stun, the blocking animation is played, stunning you briefly. If it would not have caused a stun, then you get a "free" block with no animation.

One more important thing :
If you cannot be stunned, the block animation will never play.

So if your build use Unwavering Stance you don't need block recovery, cause you will never trigger the block animation.