SSE mode

Thats true, but it's like the story that Smash Bros. Never had. Subspace Emmissary is a semi-roleplaying adventure where you play as a certain single or group of characters battling hordes of subspace enemies (and the occasional Mario baddie and evil Smash bro.) The point of it is to collect all of the enemies as trophies and to find all of the secret doors and Gold boxes. And if you play it, it's 10x easier to unlock characters (play through once and all but three characters are yours!)

Hope I clarified

Adventure mode

SSE means Subspace Emissary also called the Adventure Mode. People say the brief meaning just because it's too long to type. It's somewhat of a role-playing game where you get to fight characters,enemies,and bosses. Subspace Emissary comes with trophies,stickers,and CD's to boost your collection. It also helps you unlock characters without fighting them(Well for some characters you have to fight). The Subspace Emissary is known to be thrilling and exciting. You can unlock almost all the characters just by beating it once! Trust me. You wanna get all the characters quickly. Hope this helps.