Poser's native pose files can store animation data, much like Biovision's BVH files. Both filetypes are text format, and can be edited with Notepad and other utilities, but the data isn't organized in the same manner, so they cannot be used interchangeably. The file shown in your image above is a pose file, so give it a .pz2 extension, put it in one of your Pose folders, and load it from the Pose Library. If it were a BVH file, you'd simply give it a .bvh extension and import it from the File menu.