Encoding and transcoding are often confused, due to how similar they sound. In fact, both are done for the same reason: reducing the size of the video, and making it work on more devices and on a wider range of internet connections.

The key difference, however, is in the source file:

• Encoding means turning raw video data (an uncompressed file) into a compressed format;
• Transcoding means turning an already compressed video file into a different format.