Tu Quoque (pronounced too-kwo-kwee), translated literally means "you too." This fallacy also is known as the appeal to hyprocisy. It commonly is employed as an effective red herring because it takes the heat off someone having to defend their argument and instead shifts the focus back to the person making the criticism.
It recently has been used by those defending Hillary Clinton's email-management practices. When she is criticized by Republicans, her supporters have pointed to Republican government officials who did the same thing (or something similar).
This type of argument is fallacious and should be avoided.