Xmodulo posted a tutorial about setting up HTTPS in Apache web Server on CentOS

Web servers use HTTP by default, which is a clear text protocol. As the name suggests, a clear text protocol does not apply any form of encryption on the transit data. While the HTTP-based web server is very easy to set up, it has a major drawback in terms of security. Any "man-in-the-middle" is able to see the content of the transit packets with carefully placed packet sniffers. Taking the vulnerability one step further, a malicious user can even set up an impostor server in the transit path, which then pretends to be the actual destination web server. In this case, end users may actually communicate with the impostor server instead of the real destination server. This way, the malicious user can trick the end users into handing over sensitive information such as user name and passwords through carefully crafted fake forms.

To deal with these kinds of vulnerabilities, most providers often prefer HTTPS in their web servers. For read-only type sites where users only read the content and do not actually input any information, HTTP still is a viable option. However, for sites that maintain sensitive information and/or sites where users log in to get services, HTTPS is a must. HTTPS enables a website to provide the following services.

  How to set up HTTPS in Apache web Server on CentOS