: This refers to the audio format . It stands for "Dolby Digital 5.1" surround sound (five speakers and one subwoofer).
: This is the video codec used to compress the file. It is one of the most common formats for high-definition video.
: This is the name of the release group (the people who ripped and shared the file online).
The text you provided is a standard for a digital movie file. It uses a specific naming convention that tells you exactly what you're looking at. 1080p.WEB-DL.DD5.1.H.264-EVO" means: