Macnchaboi if you watch the film posted by TWM5043 true Frottage happens from about the 12th minute the rest is just erotica. Frottage is like fucking but without the penetration, some will do mutual cock wanking - so 2 cocks in hand with the cocks on top of each other - that feels great, or like in the vid, cock rubbing against the body and between the legs and over the arse also feels great!!
Whilst cum does not get inside, the risk of HIV infection is very low unless you get HIV cum all over the glans and urethra like in this vid so there`s the potential for HIV transmission if someone has the virus of course, but there is of course the risk of syphilis, herpes, warts, crabs and scabies because they are transmitted by skin contact. And lets not forget chlamydia and gonorrhoea if you`re rubbing cocks together or rubbing cock over anus.