It’s very confusing at first glance, but I’ll try to help clear that up.
Alliances and Partner Airlines
Frequent flyer miles are a rewards program for flying with a specific airline or alliance. An airline is pretty clear about who they partner with and their alliances. A partner could be an airline that is outside of their alliance.
For example, Alaska Airlines is not in an alliance (such as OneWorld, SkyTeam or Star Alliance), but they partner with British Airways, American Airlines and more.
The alliance/partner relationship between these airlines allows you to focus your rewards in one program, while being able to fly any of the partners/alliance. This means that if you take a flight on British Airways, you could credit those miles to Alaska. When you accrue enough miles to Alaska for an award flight, you could book an award flight on American Airlines. That booking is open to any of the partners saved those rewards with. In this example, it’s Alaska Air.
TIP: When you fly, you’ll want to focus crediting your miles to a specific program so you can redeem an award flight much faster.
The Three Main Alliances