Order Resources are similar to the garrison resources in WOD patch, which are used for learning Class Order Hall upgrades, Seal of Broken Fate exchanges and so on.

However, How do I get Order Resources?
1. World Quests: This is the most reliable source of Order Resources, mainly due to the huge amount of world quests that can potentially grant you resources as a reward. The reward includes WOW Gears, Blood of Sargeras, Artifact Power and order Resources. Also, Emissary Caches will give you Order Resources. Every day you will get about 5000*Order Resources based on the World Quests.
2. Class Hall Campaign: When you first start out on your campaign, you will be granted enough Order Resources to ensure that you can complete all the missions that you are given to do for the campaign.
3. Kill the rare bosses and pick up chest will get Order Resources.

There is no upper limit to farm Order Resources. So, What are the usages of the Order Resources that we have worked so hard? Order resources have a number of uses, including:
1. Upgrade Artifact Knowledge Level. Artifact Knowledge level research needs of Order Resources are fixed, each level needs 500 resources, 5 days in total. Also, Artifact Knowledge level is a valid way to accelerate Artifact Power gains and unlock more Artifact Traits.
2. Upgrade Class Order Hall Level. Players will equip 2 Legendary gears when Class Order Hall level at the top level.
3. Upgrade Class Order Hall Gears Set, complete follower missions, recruit class order hall followers, exchange Seal of Broken Fate and so on.

Maybe you will know much a lot for Order Resources after reading this introduction.