On Summoner’s Rift, a team wins by destroying the enemy Nexus.
The Nexus is the large core structure inside a team’s base. It is the final objective of the standard five-versus-five match: teams push through three lanes, break defensive turrets, and usually destroy inhibitors before they can damage the Nexus safely. Two turrets directly guard each Nexus, so reaching it requires coordinated attacks and control of the surrounding base.
The other options describe important structures but not the winning objective. Turrets defend lanes and bases, while inhibitors block each lane and temporarily prevent the enemy Nexus from being attacked until the necessary defenses are down. A fountain is the team’s home area, where champions respawn, recover, and buy items; it is not a victory target.
The Nexus also has a gameplay role beyond being the objective. Each team’s Nexus periodically generates minions, which march down the lanes toward the opposing base. Destroying the enemy Nexus ends the match immediately, although games can also finish earlier if a team surrenders or forfeits.