The main adventure is the challenging quest that your party undertakes. For DMs who don’t homebrew, this quest takes the form of a “module”. That module usually has some type of “dungeon”. The dungeon might not literally be a prison, but it is usually some underground place with monsters, traps, and other challenges, the conquering of which is rewarded by treasure. Good role-playing means that the adventure doesn’t begin at the entrance of the dungeon. Rather the adventure starts at some type of home base, like a town not too far from the dungeon, where the characters can eat, sleep, and buy weapons, armor, and equipment. This home base often becomes the center of the campaign, which is the geographical/chronological/political setting in which all of the adventures take place. A side adventure is usually in such a town or very close to the town. It is usually much shorter than a module. In Morgran’s case, this can involve using his gaming skills on some merchants to raise money for weapons and armor. If he is not of good alignment, he can use his Sleep Spell on those merchants to rob them. A lot of the role-playing that happens in taverns, including the classic tavern brawl, could be classified as a side adventure.