SSL is built into all major browsers and web servers, simply installing
a digital certificate turns on their SSL capabilities.
There are two certifications :
Authenticate your site. A digital certificate on your server automatically
communicates your site's authenticity to visitors'
web browsers, confirming that the visitor is actually
communicating with you, and not with a fraudulent site.
Keep private communications private.
Digital certificates encrypt the data visitors that exchange
with your site to keep it safe from interception or tampering
using SSL (Secure Sockets Layer) technology, the industry-standard
method for protecting web communications
Requiring registration and passwords lets you keep track of visitors,
but if exchanging this information isn't secured, data can be intercepted
online. Fortunately, personal certificates can help. Not only do
digital certificates help you secure e-commerce transactions with
visitors, they can also help you learn more about your customers
and enhance their online experience.
Instantly authenticate a visitor's identity, instead of requiring
individual usernames and passwords.
Different companies like VeriSign etc assign certification.