The main reason to use an SSL certificate on your website is to secure sensitive information sent across the Internet. Keeping data encrypted so that only the intended recipient can understand it.
This is important because the information you send on the Internet is passed from computer to computer to get to the destination server. Any computer in-between you and the server can see your credit card numbers, usernames and passwords, and other sensitive information in plain text and easily readable if it is not first encrypted using an SSL certificate.
When an SSL certificate is used, the information becomes unreadable to everyone except for the server you are sending the information to. This protects you from hackers and identity thieves.
For example when you visit an ecommerce website to view their catalogue. When you’re ready to order, you will be sent to a order form or checkout with an address that starts with https://.
When you click “Send”, to submit your order details back to the retailer, your browser’s HTTPS layer will first encrypt the information. At the other end only the website which knows the SSL encryption can decrypt your information and use it to complete the purchase.
The acknowledgement you receive from the server will also travel in encrypted form and arrive with an https:// address that can be decrypted for you by your browser.