what is the meant by vaccum?what is the use of vaccum pump?

Vacuum is space which is devoid of matter.Vacuum is a region with a gaseous pressure much less than atmospheric pressure.In engineering and applied physics on the other hand vacuum refers to any space in which the pressure is lower than atmospheric pressure.
A vacuum pump is a device that removes gas molecules from a sealed volume in order to leave behind a partial vacuum.Vacuum pumps are used in many industrial and scientific processes including composite plastic moulding processes,driving some of the flight instruments in older and simpler aircraft without electrical systems,production of most types of electric lamps,vacuum tubes,semiconductor processing,electron microscopy,uranium enrichment,medical applications such as radiotherapy, radiosurgery and radiopharmacy etc.