SSL:

SSL is known as secure socket layer. It provide standard security for encrypted linkbetween server and client like website, browser, mail server etc.

SSL allow sensitive information such as credit card number, Social security number and login credentials to be transmitted securely.

When we send the data from browser to web server it send in plain text mode that time attacker can intercept all the data and can see the data and information.
To avoid this vulnerability we use SSl certificates. After activate SSL certificate when we send data from broser to web server it convert the plain text into the SSL algorithm which encrypt the data and information both over the network.
SSL secure lots of peoples data and information over the network every day especially during the online transaction or transmitting the confidential information.
If SSL has activated then it comes in green in address bar.

Where do certificates come in?

All browsers have the capability to interact with secured web servers using the SSL protocol. However, the browser and the server need what is called an SSL Certificate to be able to establish a secure connection.

Work of SSL certificate?

SSL certificates have a key pair:
Public Key and Private key
This both key work together over the network or browser to encrypt the connection.