CIDR = Classless Inter-domain routing
Basically when IP4 was new, it was classful. Meaning that networks were part of classes that were fixed in length. You'll see these classes reffered to as Class A, B, C, D, E netblocks.
When the Internet started growing they quickly realized they had to move away from classful networks to get better number utilization.
CIDR allows you to have a routable subnet of a classful network.
Route Summarization is just the act of summarizing multiple subnets into an aggregrate to lower the processor and memory overhead of the routers.