A guy explains something to his friend.
A guy explains why he can't attend a event with his friend.
Both sentences refer to a guy. However, we only know that the guy explains something to his friend. The word "something" does not infer why he can't attend an event with that friend. In order to infer these details, the words "event" and some key words that help us infer he will not be attending the event.
(-x)
(-x)