Definition - What does Plea mean?
A plea refers to an answer to a claim made by an individual in a criminal case in an adversarial system. Colloquially, a plea has taken on the meaning of a declaration made by a defendant at an arraignment, or in response to a criminal charge, wherein the defendant claims him or herself to be guilty or not guilty. Most jurisdictions also allow for a person to plead "no contest."
Justipedia explains Plea
The idea of a plea is one of the most significant differences when comparing criminal and civil procedures. Under criminal procedure, a plea of guilty by the defendant waives the trial process and allows the defendant to be sentenced immediately. On the other hand, in civil procedure, there is no concept of a guilty plea. Even if a defendant is willing to give a full confession, this will not prevent a trial from being held, nor does it relieve the plaintiff from the duty of proving its case.