OEM..help!

I recently was looking at a few software programs from a site, and it said OEM. It stands for Original Equipment Manufacturer. Does this refer to its original, or does it mean the site made it and are selling it? Is it illegal to sell these on eBay?
Someone please help..thanks.

oem means that it's made from the actual manufacturer. say microsoft has a product and you see an oem microsoft product on ebay. that means that the product is made directly by microsoft

I will agree that OEM mean original equipment manufacturer

OEM is just that product. You don't any instruction manuals or accessories or whatever you get when you by the product brand new.