SSL stands for Secure Sockets Layer, the SSL certificate displays information to verify the owner of a website and encrypting web traffic with SSL/TLS — including the public key, the issuer of the certificate and associated subdomains. And SSL, commonly known as TLS, is a protocol for encrypting Internet traffic and verifying server identity. All websites with an HTTPS web address uses SSL/TLS.
It's very important that you have an SSL certificate on your site to instill user's trust: you need it to keep user data secure, verify ownership of your website, and to prevent attackers from creating a false version of your site.
Authentication :- SSL certificates verify clients that owns the domain. This prevents domain attacks and spoofs.
Encryption:- SSL/TLS encryption is possible via the public-and-private key pairing that facilitates SSL certificates. Clients get the public key to open a TLS connection from the server's SSL certificate.
HTTPS :- SSL certificates are required for the HTTPS web address. HTTPS (the secure version of HTTP) appear on websites that have traffic encrypted by SSL/TLS. Plus, in addition to securing user data, HTTPS displays a credible "trust factor" from the perspective of the site visitor.