can somebody tell me what for a Machine this is and what is its function?

It is a 3 axis Milling machine, similar to a drill press in design, but unlike drill presses that drill only, this machine drills, and usually has a cutter (called a mill) of some sort mounted in the spindle(not shown), then on the bed(bottom) you have a hard vice that moves in both x,y direction, the cutter (moving in the z direction)cuts the material usually in increments of .001" or larger, depending on the operator. Making the material precise and flat. Milling machines are used to "carve" out parts, like gun parts, engine parts, transmission parts, etc.