The casual mode we'll all start with...
Turf War: Paint the map. Team with the most area covered in their color after 3 minutes wins. Walls don't count. I repeat - walls don't count. Obviously killing opponents helps win, as the time spend respawning is time not spend painting. But some weapons are so good at covering a lot of turf fast, they don't need to kill. Others need to kill them. In practice games often come down to whoever can get a wipe or partial wipe 30 seconds from end.
Ranked modes are unlocked after a while, if Splatoon 3 keeps the tradition of the previous two...
Splat Zone: Teams try to keep control of a marked area of the map for a certain amount of time to win. Control is gained by painting over the other team's color. This mode keeps the basic concept of Turf War and condenses it into a tinier space, making the mode more focused on taking out opponents before painting; at least if your weapon has worse ink consumption or less range than the other side who's able to paint over your color from a safe distance with greater efficency. Or, if you're more the not so aggressive type yourself, you pick one of those defensive shooters, too.
Tower Control: You ride a tower along a pre-set track into the other team's base to win. Painting doesn't factor into the win condition directly, but you'll still need to kill and paint key points of the map to gain control of the fight, for example around a choke point the tower may have to pass through. If no team has reached the other's base by the 5 minute mark (the timer for all ranked mode compared to Turf Wars 3 minutes), the team that came closest wins. But games don't end as long as at least one member of the currently losing team is still on the tower, which frequently leads to exciting last ditch pushes for those last decisive inches. Similar overtime nailbiters can happen in the other ranked modes, though never in Turf Wars which always end on time.
Rain Maker: You have to carry the rainmaker into the other team's base to win. The rainmaker is a weapon. Carrying it slows down the wielder, but in exchange they get to fire off huge nukes made of ink to clear a path. Due to the slow charge time, they still require heavy support from their teammates. Think of Rainmaker like a reverse Capture the Flag with a flag that snares the carrier but fires off mortar strikes. Painting the map is important here because Inklings, including the holder of the rainmaker, move faster through their own ink.
There was a fourth ranked mode in Splatoon 2, but I'm not sure it'll make a return. And we'll probably get at least one new mode in Splatoon 3 that hasn't been in the games before.
And on the PVE side, in addition to the story campaign...
Salmon Run: A horde mode which has you take on waves of enemies in co-operation with three other players. The goal here is to survive waves of enemies and bring a special kind of item dropped by the bigger, more dangerous mobs back to a stationary collecting spot. Enemies leave their own trail of ink, hindering players' movement while returning their cargo, so you can literally tell by the color of the ground when you're getting overwhelmed by the continuing flood of enemies.
Important to note that the ranked modes and Salmon Run are available on a set rotation in Splatoon and Splatoon 2, while Turf War can be played at all times. Although we haven't gotten confirmation one way or the other, as far as I know, this will likely not change in Splatoon 3.
