Sender: Sender is someone who caused something to be sent to a recipient. 

An example of a sender is the person who put a letter in the mailbox.

Receiver : Receiver in  electronics, any of various devices that accept signals, such as radio waves, and convert them (frequently with amplification) into a useful form. 

Examples are telephone receivers, which transform electrical impulses into audio signals, and radio or television receivers, which accept electromagnetic waves and convert them into sound or television pictures.