A graduate school (sometimes shortened as grad school) is a school that awards advanced academic degrees (i.e. master's and doctoral degrees) with the general requirement that students must have earned a previous undergraduate (bachelor's) degree with a high grade point average. A distinction is typically made between graduate schools (where courses of study vary in the degree to which they provide training for a particular profession) and professional schools, which offer specialized advanced degrees in professional fields such as medicine, nursing, business, engineering, speech-language pathology, or law. The distinction between graduate schools and professional schools is not absolute, as various professional schools offer graduate degrees and vice versa.

Can we conclude that is graduate school the same as a masters degree?
no