FLirting vs cheating. This line can be close. Perhaps a way to determine it, is whether you'd be comfortable with a lover of yours doing the behavior you're questioning? You can ask yourself why or why not. Sometimes flirting alone (usually verbal banter only) can make your partner jealous or hurt, though. Many people define "cheating" as physical sexual contact, but there are romantic affairs that are emotional only.
Flirting vs cheating. Flirting usually is verbal, cheating is physical and u know what I mean!
Physical intimacy. When physical intimacy occurs, the line is crossed. This includes kissing & touching genital/breast areas (even through clothing). A hug or holding hands does not cross the line into cheating, but if these make you uncomfortable, you need to say something right away!