I understand that if a creature that has been declared as blocking is removed it will still "block" the attacking creature it declared it was blocking (Comprehensive Rules for Declare Blockers Step, 509.1h). However, what does this mean if the attacking creature has double strike? Does it hit the "ghost blocker" twice? My question extends to other abilities such as lifelink. Is the damage still dealt and life still gained?

I guess my fundamental confusion is, I don't understand what the "ghost blocker is". Can it just be understood as a 0/0 with no abilities?