Harassment

Harassment (or Harass) the act of constantly disturbing an enemy champion in his tracks while giving him hardly to no chance to counter this (and usually punishing all attempts to do so). The harassing champion receives minor advantages in the process which sum up on the long, granting early- and midgame-superiority.

Methods of Harassing
It is possible to harass enemy champions by using normal attacks or certain abilities. Thus, not all champions are potent of harassing effectively. The basic ways to harass are:
 * "Kiting". By simply having a higher attack range, you can constantly land "free hits" on the enemy champion and just retreat each time he tries to close up in order to counter-attack. This can as well be done with high range abilities.
 * "Hit and Run". Melee-champions who feature abilities to quickly dive in and out of combat can harass by getting into range, land a few basic attacks or abilities and then retreat before the enemy champion can react (such as 's ). This works best if you know that the enemies abilities which would punish getting close to him are on cooldown.
 * Zoning. Use abilities to impede the enemy's positionion or to force him to either move to or retreat from a certain location. An easy example is's . Also see Zoning.
 * Debuffing. By repeatedly applying Crowd Control to an enemy champion, occassionally combined with damaging spells or basic attacks for the duration, you can force him to retreat from combat.

Consequences
The most common goal of harassing is to force the enemy to retreat or stay at a distance. This pushes the harassed player into an uncomfortable situation: either he stays away from the harasser, eventually loosing minion kills, gold and experience, or he tries to close up and is punished with debuffs, damage or even ends up getting killed. While putting the harassed player under time-pressure (since, if harassed to long, he will be far inferior to other champions), harassing also demotivates the victim since he is hardly able to do anything about it on his own.

Countering
Since there are a variety of ways to harass, there is not one ultimate way to be safe against all kind of harass. Trying to buy items that protectfrom the form of Harrass you're facing is usually hard since killing minions to gain gold is being punished. The best ways to properly react is to either swap lanes with an allied champion who is not (or at least not as much) impeded by that form of harassment, or to ask your teammates for help and try to kill the harasser together.