In grade school, plagiarism results in a lower grade for that
paper or writing, possibly even a failing grade (F) in the higher
grade school years.
In high school, plagiarism on a major term paper could result in
failing the subject for the year. High school students are expected
to (1) know what plagiarism is and is not, (2) to abide by the
rules for using other people's works and (3) to know how to ask a
teacher for more explanation if needed.
In college or university, as an undergrad plagiarism can result
in academic disciplinary action as well as a failing grade, either
for that paper or for the entire course.
For Dissertations at the Master's Level, plagiarism would be
totally unacceptable. The student's Advisor would likely spot
plagiarism quickly. The student would not be permitted to defend
(sit for "Orals") with a dissertation containing or riddled with
plagiarism. Even one instance of plagiarism would call into
question the student's honesty and professionalism. The rules that
apply while "in school" also apply to professionals in the
workplace or in academic circles.
Legally, the copyright holder can bring a Civil lawsuit against
the person who has stolen the work.