The verb "stop" in the English language can be used with a gerund and an infinitive. The word "stop" has different meanings depending on how it's used. Look at the sentence, "I stopped eating fast food." Stopped is used in the past tense and eating is a gerund, or a word that describes an activity and functions as a noun. Look at the sentence, "I stopped to eat some fast food." In that sentence, there is an infinitive. The first sentence means I no longer eat fast food. The second sentence means I stopped, presumably a vehicle, and went into a place like Burger King and got some fast food. "I stopped smoking cigarettes" means almost the complete opposite of "I stopped to smoke a cigarette." Likewise, "He didn't stop talking on his cell phone" means something different than "He didn't stop to talk on his cell phone." The gerund and the infinitive make the difference.