Harrasment is used to limit an enemies xp/cxp gain allowing you to gain an upper hand in the mid to late game..
Harassment can be done in many ways, so long as it limits your oppenents growth:
- Prevent your oppenent from scoring minion kills by blocking their attacks (best done with steel and other tanky hero's).
- Attacking them directly and forcing them to pull back.
- Continuous use of CC effects to stun, root, or push them away.
- Poking with high damage abilites.
Becareful who you use these tactics on, Tanks and other high durability hero's may not be too affected by your attacks or poking. especially mid game.
Harassment is primarily useful early game but don't over use it, as harassment can limit your own growth if used too much.