I am very curious. I read somewhere that you can't contract HIV/AIDS by kissing.

But the same article mentioned that toothbrushes should not be shared. How exactly is the virus spread through anal sex? Will it only happen if there is a cut or tear in the rectum? In that case, does that mean that if both partners have cuts in their mouths, it is possible to spread the virus through kissing?

I'm sorry if I sound ignorant, I've tried to find the answer but generally, no articles provide the information I'm seeking.