what is difference between CIDR and subnetting? to me it seems to be the same but the way of writing is different, please correct me if I am wrong.
VLSM is certainly one of the essential components of classless addressing and subnetting. And summarization usually goes along with that.
Summarization allows us to more efficiently describe what we have in the network and to reduce the size of the routing table.
So yes I would agree with what you said.