Depending on the context, there are a few different consequences that may occur. For example, the consequences of plagiarism with a project at a university will be larger and different than in your notebook at home.
However, here are some realistic consequences that could happen because of plagiarism.
➜ A lower grade
➜ Automatically failing the assignment or class
➜ Academic suspension or probation
➜ Academic expulsion
➜ Legal repercussions
➜ Your work being destroyed
Many universities (or colleges) will have their policy on plagiarism visible to their students. If you attend high school, you likely can find out their policy too. Again, depending on the context, the consequences will likely be different.