What is a felony plea sentence?

Your question is somewhat confusing.  A felony plea sentence just means that the Defendant was charged with some kind of a felony.  A defendant has an option of going to trial (if the person pleads not guilty to the charge) or entering a plea of guilty or "no contest" rather than go to trial.  Usually a guilty or "no contest" plea involves a negotiated plea bargain -- but not always; a person can plead to a felony charge without the benefit of any negotiated plea deal).  Upon pleading guilty or "no contest" to the felony charge, the judge imposes a sentence.  If the charge to which the person pled was a felony, then that would be a "felony plea sentence."