What Is A "grind Spot"?

Hi everyone in this awesome server :D
I'm not new at all, but I don't know what are the Grind Spot, I only find monsters in thouse points, is that it objective?
Maybe is because I don't translate right the name (Yeah, I'm spanish xD)
Well, if someone can answer my question, I will be very thankful.
Bye :D/

 

If you're referring to the locations on the map marked by the symbol of a blaze powder, those are locations where special mobs spawn. These mobs have a yellow star next to their name. They give a lot of XP, but don't drop emeralds and gears, and they are also very powerful. Visiting these areas is optional, but you may want to attempt to gain XP here if you're up for the challenge.

 

OOOOOH, that makes a lot of sense, thank you very much