Data in transit is data being sent over a network connection. Data encryption in transit is required to prevent a "man-in-the-middle attack", when an intruder is able to gain information from "listening" to the network traffic being transmitted in clear text. Protocols such as HTTP and Telnet send data in clear text, while protocols such as HTTPS and SSH encrypt the data in transit.
To enable HTTPS, you need to create a public-key certificate, signed by a trusted Certificate Authority (CA), to confirm that the certificate holder is indeed the owner of the domain that presents it. The newer protocol most commonly used today to encrypt HTTP traffic is TLS, however, the certificates are still commonly referred to as ...
