Secure Sockets Layer (SSL) is a security protocol that provides cryptographic protection of information during transmission. SSL’s main purpose is to create and maintain an encrypted link between the client and server.
It is is one of the earliest encryption protocols for securing communications on the internet, but it was developed before the widespread usage of smartphones
What is HTTPS?
HTTPS appears in the URL when an online site is secured by an SSL certificate. You can see this by clicking on the green padlock image on the browser bar. HTTPS is so common these days, that Google expects it from webmasters. Look at the SERP pages and you will see that most pages in the Top 10 have SSL installed.