Even when it comes to e-mail, g-mail, any-mail… and more, including in the cloud Imagine your attic has an extra door that you share with a nosy neighbor. Usually it stays closed (the door, of course). Closed doesn't (always) mean locked. Because neither you nor the neighbor has the key. You assume that your neighbor doesn't sneak in your house, but how would you be able to tell if you are down in the living and the upstairs door is open (not locked)?
This is pretty much the principle that led to the HTTPS (Hyper Text Transfer Protocol Secure) - to protect you and your data from nosy people (not necessarily limited to your neighbors).
HTTPS stands for the use of an ordinary HTTP over an encrypted Secure Sockets Layer (SSL) or Transport Layer Security (TLS) connection. When a user connects to a Web site via HTTPS, the Web site encrypts the session with a digital certificate, and establishes a secured connection which makes it impossible for a third party to eavesdrop.
Why should that be so important? Coming back to the nosy neighbor, would you like to have him in upstairs when you call at the bank to check your balance and have to go through that procedure where you recite you name, address, card number, password and so on? Probably not. HTTPS is the protocol you would like to use when you check your e-banking and e-commerce account or when you purchase goods and services on-line. But what about e-mail?