What is Digital Mobile Radio (DMR)? It’s an open digital radio standard that can be used by amateur radio operators to use digital infrastructure such as the Internet to provide communication.
Want to know more? Here are some resources to help you along your learning journey!
Wikipedia
https://en.wikipedia.org/wiki/Digital_mobile_radio
The best podcasts on the subject to date
http://hamradioworkbench.com/hrwb045-dmr-basics-part-1
http://hamradioworkbench.com/hrwb046-dmr-basics-part-2
Podcasts are simply readily accessible audio or audio-video files that can be played on mobile devices through special programs, or web browsers. For more information on how to use them, here are some helpful links.
https://www.howtogeek.com/345845/how-to-get-started-listening-to-podcasts/
https://www.wired.com/story/podcasts-beginners-guide/