Maxis Match is CC that matches the same art style that ships with the game ..... cartoony, skins have the same smooth cartoon look, clay hair, bright colors, clunky chunky furniture, everything written in simlish, etc.
Alpha CC refers to CC that uses more realistic textures ... hairs are wispy like RL hair, skins are hyper-realistic with pores showing, wrinkles around the eyes, some of them even have stretch marks, clothing is much more detailed and actually 3D moddeled, instead of just "drawn on" detailing, same thing for furniture and deco objects. TS4 art style "fakes" it alot with drawn textures on a lot of things, like some kitchen cabinetry has fake handles (which looks ok, until you look from the side and realize there is no actual handle), same thing cabinet drawers or doors, they're fake, just made to look like there's actual definition when there isn't any.