MKS system means Meter Kilogram Second based measurement system. Where length is measured in meter, weight is measured in kilogram and time in second. But it does not mean that we have only these three units but it means that all units are based on these three base units.
First proposal of MKS system was given by Giovanni Giorgi in 1901. Historically the use of the MKS system of units succeeded the centimetre–gram–second system of units (CGS) in commerce and engineering. The metre and kilogram system served as the basis for the development of the International System of Units, which now serves as the international standard.