Delves are micro-dungeons that a solo player can easily complete. Every delve houses a Skyshard and a delve boss. Each delve in Summerset (and the one on Artaeum) has at least two quests tied to it. Some of the main story and side quests on Summerset will push you through a specific delve, but the two quests per delve we’re referring to specifically take place inside their respective delve.
You can always find one of the quests in front of its related delve, while the other quest is a daily that you must pick up from Justiciar Tanorian in Alinor.