Acceptance of plea

What does Acceptance of plea mean in American Law?

The definition of Acceptance of plea in the law of the United States, as defined by the lexicographer Arthur Leff in his legal dictionary is:

When the defendant in a criminal action seeks to plead guilty, that plea must be made to a judicial officer for his formal acceptance. It is the duty of the judge to ascertain that the plea was made voluntarily, not under coercion, and increasingly of late (especially in the federal courts) accurately, i.e., that it is not a plea of guilty to something not done by the defendant, offered by him solely to avoid the risk of conviction of a more serious offense. See plea bargain.