Story

Unlike most games, DDO does not have a main quest that you can follow, no overarching storyline that would guide you through the game content in order. Instead, DDO works with the concept of Adventure Packs, collections of quests that are connected by theme, location, and/or storyline.

A very similar concept to adventure packs, Story arcs also group quests by a storyline. Completing all quests in a story arc often yields special chain rewards. The main difference is that some adventure packs include also stand-alone quests. Another difference is that adventure packs are also things available for separate purchase for free or premium players (VIP have access to all packs except expansions). Story arcs may sometimes arc over several adventure packs.

Sometimes, several related adventure packs are grouped in Sagas. Completing all quests in a saga again yields an extra reward.

What content to run
If you are a new player and don't know what to run, you can for example consult the list of Quests by level and XP. Because of bravery bonus and the way over-level penalties work, many players run quests up to 2 levels below their character level (for example, run Keep on the Borderlands quests at character level 3 or less; or run Ruins of Gianthold around level 15 or 16).