Long story short, while all of them are the very same person, consider that:
Ganondorf is a Gerudo who wants the whole triforce and this makes him the villain. He has the look and personality of any humanoid.
Ganon is the name given to any of his strongest transformations (whether OoT, TP, Oracles.. you name it). He can still think and process emotions yet he's basically Ganondorf at his fullest (Demise's got to do something here but not that crucial so far in the oficial story)
Calamity is still Ganondorf.. yet he's lost all human(noid) characteristics; he doesn't feel, not talking, not thinking, not reasoning. He's Ganondorf totally defeated and consumed by his own power, greed, and hatred (and Demise's will maybe?). Consider BotW is over 12000y beyond his first appearance in OoT.
Hope this helps. Source: I'm over 25 and I've played EVERY ZELDA GAME