What is a strut bearing plate?

The top of the strut is connected to the vehicle body through the upper strut mount, in some cases called a bearing plate. This bearing plate allows the strut to pivot as the wheels are turned. It must be flexible enough to handle slight angle changes and dampen movement of the upper end of the strut. This mount or bearing plate transfers vehicle load to the strut and spring, making the upper mount/bearing plate the load carrier and the lower ball joint the follower.

I found this on the Monroe site.