Once an enemy team's inhibitor is destroyed, the Nexus will start spawning Super Minions (replacing the siege minions with Super Minions if the wave normally includes one) along with giving a boost of roughly 100 health to all the melee minions, 50 to the caster minions, and 200 to the siege minions in the corresponding lane for future waves. Only minions spawned in the destroyed inhibitor's lane receive additional attack damage while the inhibitor is down.
Each team has 3 Inhibitors on Summoner's Rift and 2 on Twisted Treeline, of which at least one must be destroyed for the Nexus and its turrets to be vulnerable to attack. Every inhibitor is protected by a turret; while this turret is up, the inhibitor is invulnerable to attacks. When all of the enemy team's inhibitors are destroyed, each lane spawns two Super Minions per minion wave.
Destroyed inhibitors respawn after 5 minutes, resulting in Super Minions no longer being trained and the removal of normal minions' bonus health.
Once its protecting turret is destroyed the inhibitor is extremely susceptible to backdooring. An enemy marksman will be able to take down an unprotected inhibitor before a defending champion can recall and walk to defend it. Additionally, one can't directly to it. Destroying an inhibitor can often be worth more than a few champion kills because of the immense lane pressure that Super Minions will provide, as well as strengthing the melee and ranged minions in the destroyed inhibitor's lane (As of patch 3.14, destroyed inhibitors no longer increase the strength of all minions in all lanes).
Reward for destruction
When an inhibitor is destroyed, if a champion got the last hit, he gets 50 gold. Unlike turrets, no other members get any reward. Curiously, the Nexus is actually considered a kind of inhibitor in League, so whoever destroys it also gets 50 gold, even as the game is ending.
Unlike turrets, inhibitors do not gain any armor or magic resistance when no enemy minions are within its sight range.
Though they have no armor, inhibitors take 85% damage from champions.
Damage with autoattacks to inhibitors is based on your base attack damage plus either bonus AD or 40% of AP, whichever is higher.
When the announcer notifies that either your or the enemy's inhibitor will respawn soon, said inhibitor will respawn in 15 seconds.
The Inhibitors were sometimes referred to as "Barracks" (e.g. in detailed statistics), the name of a similar building in DotA.