ok
what is a harraser?
what is a bodyguard?

please explain the strategy without substituting words for jargen/slang

I'm not familiar with the term "bodyguard". I think he means a warrior you use as a harraser for your key warrior(s). By "key" warrior, i mean a warrior that is central to the design of your army. A harraser, in general, is a warrior whose intention is to block lines of fire and be sent into base contact w/ a particalur threat so as to prevent that threat from making a ranged attack or moving into base contact with your key warrior(s)- a distraction for your enemy, more or less.

Harrasser is usually a cheap figure and preferably with high speed value (and as stjohn5179 eloquently and accurately stated) whose intention is to block lines of fire and be sent into base contact w/ a particalur threat so as to prevent that threat from making a ranged attack or moving (or charging/surging) into base contact with your key warrior(s)- a distraction for your enemy, more or less.

Bodyguard is usually a moderately priced melee warrior that more often stays behind a few inches from the centerpiece/main attacker or other key figures. When that centerpiece is threaten (ex. base contact), the bodyguards will pound that invader away. Having an intimidating bodyguard or two nearby your centerpiece will give your opponent second thoughts on basing your centerpiece.