What Type Of Files Can Be Downloaded On A Computer?

Well any type of files which are compatible with the operating system can be downloaded and installed on a computer.

An operating system basically is a collection of computer programs which administer the hardware as well as software resources of a computer. An operating system logically processes electronic devices in reaction to standard commands given. At the base of all system software, an operating system executes the fundamental tasks like managing and allocating memory, prioritizing system requests, administering the input and output devices, making networking possible and also running file systems.  

Nearly all operating systems have the command line interpreter as the fundamental user interface, but might also offer a graphical user interface to stop certain operations. The operating system also works as a platform for other system software's as well as application software's.