What is the difference between a robbery conviction and a conviction for assaulting a security guard in a parking lot?

[16 Cal.App.4th 25] "In the instant case, since the defendant had neither ceased to threaten violence toward the victim nor had yet made his escape at the time he let the victim out of her car and drove away, there was but one act of robbery, and that occurred concurrently with the accompanying acts of theft (i.e., the taking of the victim's purse, money and car). Logically, the theft of the automobile is no more divisible from the rest of the robbery than is the theft of the money from the theft of the purse. (See People v. Estes (1983) 147 Cal.App.3d 23, 28-29 [194 Cal.Rptr. 909], in which the defendant's robbery conviction was affirmed but his theft conviction reversed where the defendant shoplifted merchandise in a store and then assaulted a security guard who tried to apprehend him in the parking lot.)