Traffic between a web browser and a web server on the internet or even within a corporate intranet is open and can be intercepted. To avoid the data being compromised, you can make use of protocols built into your web browser and IIS to provide encryption as well as authentication.
In the 1990's, Netscape Communications developed a protocol that provided the necessary security, the Secure Socket Layer (SSL) protocol. SSL V1 was never commercially released, but SSL V2 and SSL V3 were developed, released, but are now deprecated as unsafe.
Transport Layer Security (TLS) was developed openly as the next version of SSL. TLS V1 is essentially SSL V3.1. In 2014, Google identified a serious vulnerability in both SSL V3 and TLS V1. That leaves TLS 2 as the best protocol to deploy and it is the only one installed by default with IIS in Windows Server 2013.
These days, SSL as a protocol is being deprecated in favour of TLS. Most major web sites no longer actually use the SSL protocol...
