Java is a programming language and computing platform first released by Sun Microsystems in 1995. There are lots of applications and websites that will not work unless you have Java installed, and more are created every day.
IIS is able to impersonate the IUSR_<computername> account because the user name and password for this account are known by IIS. Before returning a page to the client, IIS checks NTFS file and directory permissions to see if the IUSR_<computername> account is allowed access to the file.
An exr file extension is used for images stored in the OpenEXR Image Format that was developed by the Industrial Light & Magic. OpenEXR image format was going to public in 2003 and it is supported by popular graphics applications, such as Adobe Photoshop, Adobe After Effects, 3D Studio Max, Blender etc.