The California law has codified in the penal code certain crimes known as “enhancements.” These crimes punish conduct that accompanies or occurs after a primary offense. For example, let's say that a defendant was caught during the commission or attempted commission of a felony (the primary offense) and at the same time the defendant had in his possession a firearm (the secondary offense). Here, the defendant would be sentenced based on the primary felony offense and would also face additional charges for the secondary offense based on the firearm enhancement.
PC 12022.1 codifies the out-on-bail enhancement. PC 12022.1 states that “any person arrested for a secondary offense which was alleged to have been committed while that person was released from custody on a primary offense shall be subject to a penalty enchantment of an additional two years in state prison which shall be served consecutive to any other term imposed by the court.” Here, the secondary offense does not need to occur at the same time as the primary offense. Rather, the defendant must be out on bail on the primary offense when an entirely new offense is committed.
Basically, this means that the defendant will be facing considerably more time if he commits a crime while out on bail for a different crime. As it relates enhancements in general, the punishment for certain crimes can be greatly enhanced if the crimes are accompanied by additional circumstances (i.e. committed with a firearm, committed while out-on-bail, committed a crime which resulted in great bodily injury to the victim, etc.).
Ideally, the defendant's attorney would negotiate a plea-deal that would include the District Attorney dismissing the enhancements, or, in the alternative, argue the facts before a jury at trial.