Security Certificate Files ensure that all communications on that particular website/connection are secured using a public key infrastructure. This is done through the use of small data files, known as Security Certificates or SSL (Secure Sockets Layer) Certificates, that digitally associate an organization's details together with a cryptography key. They are then installed on web servers, initiating a secure connection between the web server and browsers over the HTTPS protocol.
Most websites today are secure and have a Security Certificate (SSL) installed. You can check if a site ensures secure communication through its web address, it should have an extra “S” after the HTTP. For example, “https://www.google.com/” is a secure website.