A plea bargain is an agreement between the government and the defendant concerning the terms and conditions of a guilty plea. When a defendant accepts a plea bargain they are giving up their right to challenge or contest their case through a trial.
Plea bargains are almost always made in the best interest of the government. This is because the government is guaranteed to obtain a criminal conviction, avoids the expense of trial and does not have to risk any challenges made to the existing laws or actions of law enforcement.
Sometimes plea bargains are also in the best interest of the defendant as well. This is because the defendant can limit or negate their exposure to criminal penalties such as jail or prison time and will not have to incur the expense or uncertainty of trial.
There is no requirement that the government offer any defendant a plea bargain. However defendants always have a right to plead guilty if they so chose. Without a plea bargain their sentence will be controlled by any sentencing range called for in the law along with the discretion applied by the Court.
There are several ways a plea bargain can be structured. This may include agreements to dismiss some charges, reduce the severity of charges or an agreement on probation or the amount of jail time a defendant may face.
Before any defendant should consider a plea bargain they should fully understand the charges they are facing, what the government would have to prove at trial to prevail and what the evidence is against them. Once a plea bargain is submitted to the Court and approved by the judge it is typically irrevocable - meaning even if the defendant changes their mind later they have given up their right to a trial.