Example 1
For Brock, Thanksgiving is all about pumpkin pie. It's his favorite dessert.
In this example, dessert is the right word because we're talking about the final course of the meal. You know, the one right before you go put on your pants with the elastic waistband and watch football for the next six to eight hours.
Example 2
Miranda wants to move to the desert because of the low humidity.
The original meaning of the word desert is "abandoned place," so Miranda shouldn't have a difficult time finding an apartment. This sentence refers to a dry place with little moisture and guaranteed good hair days, so desert is just the word Miranda's looking for.
Example 3
"This play is terrible," Lily whispered. "If you desert me at intermission, I'll never forgive you, Victor."
Amateur theatre has been damaging friendships for centuries. Here, we have an example of the verb desert. Lily is telling Victor that if he crawls out the bathroom window between acts to save himself, she'll never forgive his selfishness.