Simple question, which has been prompted from this answer.
What is a bloquers?
I'm guessing it's some kind of prussik and it's a French term. But I'm not familiar with it. A quick google search returned no results.
I can only assume, that it derives from bloquer which is french for blocking. What the "c" is doing in there I have no clue - but then, I am not a native french speaker.
In this case there are several devices that are generally used for this:
It's what @imsodin said. Bloqueur is the french term for "blocker" in English. So when I talk about a bloqueur, I'm talking about blocking devices. The two that I use for ascending a rope are the Petzl basic and Petzl croll.
The use of French terms is a habit that I picked up from canyoning, which is by origin a French sport, so most of the terms used there are French.
Unfortunately I can only speak decent French, my writing sometimes sucks (since it's been 5 years that I learnt the language and only use the spoken version of it nowadays).
So long story short:
A bloqueur is a mechanical blocking device.
The reason that I prefer a bloqueur above the standard prusik is because in the situations that I need it (passing a knot during ascending or abseiling, switching from descending to ascending, ...) the bloqueurs simply work faster than the prusik.
And to fully answer the question, "bloqueurs" is just the multiple of "bloqueur".
Extra addition: the mechanical prussik
The bloquers presented above all have teeth that will (slowly but surely) damage the mantle of your rope. There also do exist other kinds of bloqueurs, for example the Petzl shunt, which is known as the mechanical replacement for the prussik. The advantage is that is doesn't damage your rope as much. The disadvantage is that it can slip when used incorrectly (training needed!).