We use "dream about" for actual dreams that we have when we're asleep, and "dream of" for ambitions. I dreamt about my old schoolfriends last night. I dream of having my own little house by the sea.

Not much of a difference, it is just that it depends on which feels better and more suitable to the sentence. Hope this helped

They mean the same. There might be a slight grammatical difference, but for us native Eng speakers the phrases mean exactly the same. Or almost the same. 99% the same.