It must have struck to you a lot of time when registering a domain name or something like that which is what is an SSL? You may not know but it is on of the most important things one webmaster can ever think about.
An SSL certificate is the thing that make an S appear in front of the HTTP making it HTTPS. The best thing it can give you is the security that it has. For the rest look at this.
Hope you understood and do let me know about your views on this.
If you think you want your website to be secured