I think he is asking what is a CD. Maybe an attempt at humor?
Speaking of humorous, I know I must be getting old. I went into Walmart to buy a cassette tape to record a live show I was engineering. (Don't ask. CD recorder in the rack was dead, DAT recorder has issues and I'm not dragging my Protools setup down there for a rap concert.)
Anyway, when I asked the young lady at the electronics dept. for one, she looked at me crazy.
"I just need one blank casette tape. Music came out on them before CDs were around. Real small version of a VHS? Got one?"
"I'm sorry sir. They don't make anything like that. Never heard of them."
Sigh...