HTTP stands for HyperText Transfer Protocol.HTTP is the underlying protocol and is used by the World Wide Web and this protocol defines us how messages are formatted and transmitted. It also defines us what actions Web servers and browsers should take in response to various commands.
HTTPS stands for HyperText Transfer Protocol Secure.HTTPS instead of acting as its own application layer protocol, it uses separate protocols called SSL (Secure Sockets Layer) and TLS (Transport Layer Security) the majority of web browsers support HTTPS for more secure Internet browsing.

SSL Stands for Secure Sockets Layer.SSL is a secure protocol developed for sending information securely over the Internet. Only the user’s computer and the secure server are able to recognize the data. SSL keeps your name, address, and credit card information between you and the merchant to which you are providing it.

To convert your website from HTTP to HTTPS you have to add a secure socket layer certificate (SSL) on your website. Normally a domain provider or a hosting service provider offers an SSL certificate for your web site. Some web hosting companies offer free SSL and others offer SSL at different prices. SSL certificate should be from a Certificate Authority (CA).
SSL for Domains: For domains, SSL is on premium price and vary from company and package

SSL for Web Hosting: Web hosting companies offer SSL certificates in cPanel or Plesk hosting. Some web hosting companies offer basic and shared free SSL Certificates in a package and advance SSL separately at different prices.SSL basically secures the traffic of your website. Search engines like Google rank up your website due to SSL activation

How to convert your web page from HTTP to HTTPS? Your website traffic will be secure if you have an SSL Certificate on your website. It works automatically and redirects visitors to the secured HTTPS version. In  there is a simple tool in cPanel through which you can activate SSL. You can simply follow the instructions mentioned below to enforce SSL for the main domain or hosting.

1.Login to your cPanel.
2. In the Domain section, click the Domain icon.

3. Clicking on a domain will open a page where you can redirect HTTPS on or off. If your domain doesn’t have SSL installed then you will not see an option to enable HTTPS. Make sure that SSL is installed and the option will present itself. Leaving it on is too much better for your visitor’s traffic.

Now your domain SSL should be active and using HTTPS.

Enforcing SSL for Addon domains
To handle redirection Linux uses .htaccess files.
Create a .htaccess file by using your control panel’s file manager. By using the following code in your .htaccess file automatically redirects visitors to the HTTPS version of your site:

RewriteEngine on
Rewrite Cond %{ HTTPS} off
^ (.*) $ https ://%{ HTTP_HOST} %{ REQUEST_URI} [L, R=301]

If you have an existing .htaccess file:

• Don’t duplicate RewriteEngine On.
• Make sure the lines beginning RewriteCond and RewriteRule immediately follow the already-existing RewriteEngine On.