Android: What is Binder Thread?

Binder thread represents a separate thread of your service. Binder is a mechanism that provides Inter Process Communication.

Let's consider an example. Imagine that you have service Process B (see picture). And you have several applications that communicate with this service B (one of this application is, for instance, Process A). Thus, one service B should provide different results simultaneously to different applications. Thus, you need to run several replicas of Service B for different applications. Android runs these replicas in different threads of the Process B and these threads are called "Binder Thread #N".

I took the picture here, where you can also read what Binder is.

"Binder is a mechanism that provides Inter Process Communication."

Binder isn't necessarily just an IPC mechanism.

All cross component traffic is abstracted from Binder, a local intent for example is a binder abstraction.