The Witcher 3 - Sidequests

Sidequests can be either very short & quick or a long string of objectives you have to tick before they are completed.

The Fists of Fury sidequest above has you wondering around Velen taking on opponents in a fist fight to become the champion , I've not yet completed the quest.

They are also a good way to explore areas you would not normally visit to find other hidden quests or rare loot.