Tom bought into the young man's elevator pitch. The phrasal verb 'buy into' is used in a figurative sense in this example to mean "Tom believed what the young man said in his short presentation." Phrasal verbs can be used in both a literal and figurative sense. Take the phrasal verb 'pick up' for example:
Janet picked up her daughter's clothes from the floor.
Mary picked up some Chinese when she was there on business.
In the first case, the 'pick up' is used literally, in the second case 'pick up' is used figuratively to mean 'learn'. Phrasal verbs can be real challenge to students. Start by learning a limited list of phrasal verbs, and then move on to taking note of phrasal verbs as you come across them in context. You can also purchase a phrasal verb dictionary to help.