SSL (Secure Socket Layer) and TLS (Transport Layer Security) are the same thing.  TSL was introduced as the successor to SSL in 1999, and was designed to resolve insecurities in the SSL protocol, but everyone still calls it SSL.

Jan 17, 2017 Update - From: Google Webmaster Central

red x through padlock showing as insecure

Effective Jan 31, 2017 Google Chrome started showing websites without SSL Certificates as "insecure".

Google’s intention is to “call out” HTTP for what it is: “UNSAFE.”  
      ~ Google's Chris Palmer

Read the full article Google Will Soon Shame All Websites That Are Unencrypted 

Aug 6, 2014 - From: Google Webmaster Central

"We're starting to use HTTPS as a ranking signal.  For now it's only a very lightweight signal affecting fewer than 1% of global queries, and carrying less weight than other signals such as high-quality content, while we give webmasters time to switch to HTTPS.  But over time, we may decide to strengthen it, because we'd like to encourage all website owners to switch from HTTP to HTTPS to keep everyone safe on the web."

SSL (Secure Socket Layer) Certificates create an encrypted connection between your website and your visitors' web browser.  This allows information to be transmitted without the problems of eavesdropping, data tampering, or message forgery.

Internet forgery has become a major problem so Google is encouraging ALL websites to have an SSL Certificate, and they are giving a boost in Search Engine rankings to websites that do have it.

There are three kinds of SSL Certificates.

http vs https showing secure and insecure

1. DV (Domain Validation) SSL Certificates

The DV Certificate is one in which the CA (Certificate Authority) checks the right of the applicant to use a specific domain name.  No company identity information is vetted, and no information is displayed.  It costs $100/yr. but BEST WEBSITES includes it with your hosting.

2. OV (Organization Validation) SSL Certificates

The OV Certificate is one in which the CA (Certificate Authority) checks the right of the applicant to use a specific domain name, PLUS it conducts some vetting of the organization.  Additional vetted company information is displayed to customers when clicking on the lock in the address bar.  This gives enhanced visibility of who is behind the site, and provides associated enhanced trust.  This SSL Certificate costs $150/yr.

3. EV (Extended Validation) SSL Certificates

The EV Certificate offers the highest level of security and is used by Banks, Government, and any other type of business that wants to convey the highest trust level.  The Certificate Authority checks the right of the applicant to use a specific domain name, PLUS it conducts a THOROUGH vetting of the organization.  This SSL Certificate is $300/yr.

With all of these SSL Certificates your website goes from http:// to https:// (the "s" indicates secure) and shows a closed padlock in the address bar.

domain name showing secure green padlock

With the EV Certificate the company name appears in the green bar in addition to showing the locked padlock.

EV Certificate showing company name