"Making out" usually refers to passionate kissing, sometimes with an element of sexual activity. However, it usually does refer to just sex. Hope this helps.

Making out... is a lot less offensive than some ways of saying it!

Michael, thanks,your words are very nice to me. This questions made me feel awkward this evening. I asked that in a language learning group this evening(of course all adults), but I was blamed by a lady. I noticed I talked about something in second language but I could not speak out in our native language indeed, I also have the wrong. Thank you again for telling me that, it make me feel better now.

I would definitely not characterize "making out" as being an offensive thing to say, or as bad words that you cannot say in public. It is the standard way to refer to the behavior. Another term that means something similar would be "heavy petting", meaning kissing with an ample amount of wandering hands. Also, please don't worry about asking questions like this. We are (mostly) adults here and this is exactly the kind of thing that language learners need to hear.