Does Anybody Know How Bill Me Later Works? Anybody That Has Bill Me Later?

umm, so i was looking through e-bay to buy some stuff and it had the option to pay through bill me later so i thought ,hey why not try it out, so i did and it said to put some information like my social security number i put it in and everything else it asked me as in my address and then it said it was connected through paypal but this is where i kinda got lost, cuz i think i do have a paypal account that i made years ago but it shouldn’t have any amount of money in there anymore , so i’m now guessing that they will bill me the payment later on… anybody know how the process actually goes, i bought a veryh nice poster hahah but i don’t want it to seem like i stold 4rm the guy that is sending it to me. i guess i should just message him right