E-Mail - Electronic Mail
It is a set of the algorithm using it exchanges Messages between One E-mail id to Another. Basically it works worldwide there are multiple E-Mail services like Gmail, Yahoo, Hotmail, etc. In Daily life, we use messenger to communicate like What's app, Facebook, etc. But in professional life we always use E-Mail.
It was introduced in the 1960s century but 1970s century it had taken the form now recognized as Electronic Mail.
The Word return before "@" is the user name and After "@"is the domain name and the word after "." defines the category of the domain.
Basically It is delivered like it breaks its data into little chunks and then it sends when it's received by the receiver mailbox it's joined by it, Using this service it became secure. Nobody can steal the data from between.