They are called P clips, they wrap around the seat stay & have holes in the tail of the P to attach to your rack. They are no where near as secure a s proper rack mounts, so be carefull how much weight you put on the rack. (Ask your LBS for advise on the reliable weight) Some ppl do use them for laden touring, but then some ppl have trouble! Should be OK for the weight you need to carry on a day ride.
Cycling never gets any easier
you just go faster