They are skilled at combat with various small weapons. Goblins are dumb, weak, ugly, but very quick. They make good thieves, and some with a high intilect make good mages. Goblins usually travel in familly tribes of eight to a dozen goblins. The tribes are usually lead by a charismatic shaman or a goblin mage.
Hit points are the number of damage points the thing can take before it dies.
Armor Check is simply another name for armor class. Exp. is the number of experience points the character wins from fighting the creature. The number after the name of the combat skill is how much points the skill costs to use. Strength applies to bonus hit points and damage points. It is also used when a character's strength is needed for a certain task.