A conviction is a judgment either by a jury verdict (following a jury trial) or by a judge (following a bench trial) that a person is guilty of a crime, violation, or infraction. A plea of guilty to the charge will also result in a conviction. Upon conviction, the judge decides the sentence to be imposed.
In almost all cases, it is advisable to enter a plea of not guilty to any charge(s) against you, no matter how serious they are, in order to preserve all your legal rights and options going forward. You should then consult and retain the services of an attorney who will advise you of the potential consequences of a conviction and to represent you in court by conducting a defense of the charges, in the effort to avoid a conviction or minimize the negative consequences of one.
In most courts, and depending on the nature and seriousness of the charge(s), the prosecutor will likely make a plea offer to a lesser charge in order to conclude the matter without the need to go to trial.
Whether or not you should accept an offer and plead guilty to a lesser or alternative charge depends on many things, including your prior criminal history (if any) and the facts of your case. The final decision to accept an offer or proceed to a trial is something you, and only you, have the power to make, upon the advice of your attorney.