The consequences of plagiarism vary depending on the type of plagiarism and the context in which it occurs. For example, submitting a whole paper by someone else will have the most severe consequences, while accidental citation errors are considered less serious.
If you’re a student, then you might fail the course, be suspended or expelled, or be obligated to attend a workshop on plagiarism. It depends on whether it’s your first offense or you’ve done it before.
As an academic or professional, plagiarizing seriously damages your reputation. You might also lose your research funding or your job, and you could even face legal consequences for copyright infringement.