Buffs

Generally, a buff refers to a temporary beneficial effect placed on the player. Depending on the ability used, buffs can either be applied on yourself, a teammate, or both. Most active buff effects can always be ended in two ways: However, some buffs have special conditions that can end their effect (Shields break after reaching their damage threshold, etc.). See below for specifics on this.
 * Expires over time (usually ranging from 1 to 5 seconds)
 * Dispelled

Attack Speed
A bonus to attack speed simply allows your character to use their abilities quicker. However, while a few champions do have this in their kit, this buff seems to only boost attack speed for one specific ability.

Fortify
This effect refers to an increase in damage reduction.

Damage Boost
A champion with this effect active will deal more damage with all of their abilities.

Healing over Time
This buff will heal the affected champion in equal increments over a small period of time. This buff will not heal past maximum Recovery Health.

Immaterial
A champion that is immaterial has no hitbox; that is, they are not able to be hit by any abilities whatsoever for the duration of the effect. Units that are immaterial can still receive healing from allies. The only exception is Lucie's Clarity Potion, which will break the status. Some abilities, such as Shifu's Fleetfoot, that grant immaterial will remove debuffs as long as the debuff will allow them to cast abilities. This means that immaterial can remove roots, snares, fading snares, Ashka's Ignite, Ruh Kaan's Curse, etc., but not silences, stuns, petrifies, or incapacitates.

Immunity
Being immune is different from being immaterial in the fact that the champion has a hitbox; they just won't be affected by enemy abilities. Friendly abilities will still take effect.

Invisibility
Renders the champion completely invisible from enemies (your team will still see you). While invisible, a champion still has a full hitbox for both enemy and friendly abilities.

Movement Speed
Champion moves faster by a certain percentage under this effect.

Shield
A shield will block all incoming damage up to a certain amount until it expires. Reaching the damage threshold beforehand will break the shield.