In many aspects, Inquisition Perks are similar to passive abilities. From the moment of unlocking, they provide you with permanent bonuses and they do not require any further actions from you. The bonuses that the perks grant vary - they can, for example, increase the growth rate of experience points, provide you with better prices from merchants, make it easier for rogues to open locks or obtain rare materials. What perks have in common is that they have an effect on the entire party.
You can unlock perks by collecting perk points. The points are awarded for the successive Influence levels, which also are connected with the Inquisition activities. A detailed list of Inquisition Perks has been provided in the chapter entitled Inquisition Management. In that chapter, you can also learn about how to amass influence and unlock new perks, as well as suggestions on the usefulness of individual perks for the entire party.