COD: Both of you could depends on either party or both party to travel to a meeting place and do your transactions face to face.

Self Collect: The buyer come to your place, pay for the item, and ciao so the seller doesn't have to spend on transportation or delivery cost. Normally this is done if the seller has his own shop or the item is rather large in dimension like a TV or Aircond or the likes of it.

Meet up: More or less the same as COD.