In this episode James and Sam discuss the rules for Stealth with a special focus on using the skill to hide in D&D. You can find an explanation of this rule in the Player's Basic Rules D&D PDF on page 60 or in the Player’s Handbook on page 177.
D&D 5e Basic PDF: http://dnd.wizards.com/articles/features/basicrules
James’ blog: http://www.worldbuilderblog.me
Sam’s blog: http://www.rpgmusings.com