i cannot find what you do with credits when you buy them. is there like a place to auction good gear, or buy lightsabers, or what. some1 please esplain

Training skills, paying re-specs, buying mounts, training mount trainings, Leveling up crew skills, Using the galactic Market, Paying for repair bills, buying consumables, buying leveling gear, and probably more stuff

thanks dude. im a sith inquisitor but im still on the training planet. and i see all these offers to buy credits, but i never really figured out what to use em for