LPT request: How to flirt/Know you are being flirted with?

I've never got the whole 'flirting' thing. I'm not very outgoing but I'm fine chit-chatting with anyone, but I have genuinely no idea how to tell if there is anything else going on. I (24m) can talk to a nice girls just fine about normal small talk-y stuff or about interest if I've any input, but that's it, I just can't get my head around the flirting part at all.

Also,I apparently have been flirted with in the past (friends have let me know after) but I'm just so oblivious to it I can't remember what it entailed. Is there a difference between having a conversation with a nice girl and her flirting that I just didn't get the memo on? Because I genuinely have no idea

I couldn't find anything in search,sorry if this is covered well somewhere else