Vikas,
CIDR and Supernetting are the same thing. This is where you can aggregate networks together into larger networks beyond their natural network boundary.
Although Supernetting/CIDR might be considered a type of summarization, “summarization” generally is considered to be constrained by natural (classful) network boundaries. The distinction is somewhat subtle. Suppose you have the following:
192.168.1.0/28
192.168.1.16/28
These could be summarized as 192.168.1.0/27 because /27 is smaller than the natural /24 boundary.
Now, if you had this:
192.168.0.0/24
192.168.1.0/24
The supernet (or CIDR) of these would be 192.168.0.0/23 because /23 is greater than the natural /24 boundary.