Default What is OEM product?

I was looking for Samsung sdxc pro 64g UHS-1 in Ebay and I found one which is cheaper than others, but its retail package is not like the others, so I sent a message to ask if it is genuine.

This is seller's answer:

"Hi there, this is an OEM product made for Samsung, which means that it's branded Samsung but an outsourcing factory made for them."

I am not sure what their answer means. Should I buy this? and does z1 support uhs-1 ?