Stop and Wait

Sends 1 packet and wait for the confirmation from the reciever of that 1 packet.
Since only 1 packet is send and recived the window size of sender and reciever is equal to 1.
Least efficient of all as only 1 packet is sent

Go Back N

Here multiple packets are sent to the reciever by the sender and the reciever sent a single acknowledgment for all of them.
It is efficient than Stop and wait but the problem is the reciver window size is 1.

Let's say frames [1] [2] [3] are sent from the sender in order and [1] is lost, then in that case even if [2] and [3] reached the reciever, the reciever won't accept it as it is waiting for the [1] hence it has to resend all the elements again from [1] that is [1] [2] [3].
A major disadvantage of this is obviously excessive retransmission of packets.

Selective Repeat

Solves the problem in Go Back N ie it retransmits only those packets that have been lost. That is why it is called " selective Repeat "
Most Efficient among the three sliding window protocols