Arc Games explained the differences between episodes and modules in a post where they announced the arrival of Rage of Bel, which is the latest bit of episodic content in Neverwinter.
Chris Whiteside, Neverwinter's executive producer, came out to explain the main differences between episodes and modules to the players. In the case of episodes, the focus is on horizontal progression and narrative experience.
In case you are not familiar with the difference between vertical and horizontal progression, the former focuses on giving you bigger power numbers - think gear score, more HP, damage, healing etc. Horizontal means different ways to play the same characters, usually through gear and other systems that offer various perks as opposed to just higher numbers.
Modules, on the other hand, offer the bigger numbers and usually serve as the sum of episodes, kind of like what a season means for a TV show.
That said, Rage of Bel episode has arrived to PC players already while Xbox One and PS4 players will have to wait a while longer. It brings new mounts, a Vallenhas elite soldier companion, vanity pets and other items but Bel and the way to get to him are probably the highlights.
Players will be able to interact with dark glyphworks which will let them go to devil insurgencies . Stopping an insurgency consists of mopping the floor with any devils around until a rift appears, only to be sealed shortly after. Each time a rift appears, there is a chance one of Bel's warlords will appear, giving the players a boss fight.
Completing an insurgency causes a new one to appear shortly after and increase Bel Rage meter. This meter is server-wide and players from all over the place can contribute. Once it's filled, you can go and face Bel himself.