Trail running is considered any run that takes place on an unpaved path that is completed outside in nature. Ultrarunning is running a distance further than a marathon.
What is Trail Running?, The Trail Hub
Happy Trails: Tips for Beginning Trail Running
Trail Running 101: What is Trail Running?
What Is Trail Running? Everything You Need To Know To Run Off
Trail Running for Beginners - Weekend Adventurers
What is trail running?
Trail running vs road running: the pros and cons of each
Seattle Trail Running Basics for Beginners
What is trail running and should we all be doing it?
Trail-Running Tips: Form & Technique
Top Tips For Trail Running Newbies
TRAIL RUNNING BASICS TIPS and TRICKS to become a better trail runner
How to run uphill
Tips for Getting into Trail Running (or Taking It to the Next Level)