What is the difference between flirting and "hitting on someone," or is there no difference?

In my opinion, flirting is innocent banter that may or may not lead to a relationship/sexual encounter. Flirting can be platonic. To me, hitting on someone usually involves an invitation (implicit or explicitly stated) for sexual activity of some sort. Hitting on someone has a sexual intent. Just my two cents.

I agree with @lonelydragon. “Hitting on” someone is most often done with sex as a goal, whereas flirting doesn’t necessarily have a goal.

Agreed.
If someone’s “hitting on you”, to me, that means that person has some kind of intention/expectation of going a little further than just having conversations with you if you know what I mean.
I am a flirt myself but I never hit on anyone.

“Hitting on someone” is aggressive flirting. Flirting is subtle gestures and remarks that hint your feelings towards another person, where “hitting on someone” is just walking over and outright blurting out how you feel and what you want to do to someone. Thats my take on it.

Stay with me on this, ok. Really its all sex just different levels and different shades of gray, whether lust, or playing with sexual tension or outright seduction. When I flirt Im saying I admire you, thats all, but its a game that can go to various levels, I choke if it goes beyond the initial complement, but somewhere on some level I,m looking for feedback that I have sex appeal to you by your reactions. I wrote a poem one time that included the follow line: “I look in your eyes to find life and desire, I look into your eyes to measure myself.”

Flirting is betting, bluffing, assessing the game…Hitting on someone is going “all in” and calling. ;-)

Ya, expressions of interest vs out right expressions of desire. One follows the other with a good lead.

When it’s flirting, I’m involved as well…when you’re hitting on me, I’m not amused.

Flirting is a pleasant game when everyone knows the rules. Of course, the rules are unspoken, so sometimes people get confused and think that flirting is an invitation to something more, when it’s really just for fun.

Hitting on someone really isn’t in the same ballpark at all. It’s about picking someone up. It’s about seeing if they might like you enough to get intimately involved with you, whether that involvement is a one night stand or something more (usually the former).

Now I would never flirt with @Simone_De_Beauvoir because she’s way too serious for me ;-)

I personally think flirting is just a woman’s way of hitting on someone, although usually when someone says that they were hit on, it has a negative connotation as if it was not very pleasant whereas flirting is usually innocent

I think that they are both the same thing because if you think about it if someone is hitting on you they are flirting in a way.