Downloads for MAC

okay, so my photoshop CS trial just ran out, i was hoping i could try out psp or another program, but when i tried to download it it first of all said nothing about what type of computer you have to have, and then didn't work after i downloaded it. So im wondering what programs they have for macs? is photoshop the only one? and if it is, is there another version of photoshop i could download for the trial version? buying is not a financial option right now.
i checked the memories, but im really really sorry if i glossed over a really obvious answer.