What are intents?

Intents are a set of sample utterances and optional slots that represent a user's request.  Think of them as inputs just like buttons for a GUI or keys on a keyboard.

They can be simple, such as a YesIntent which contains the following sample utterances:

yes
yes please
sure
yup

or complex as an intent to search for recipes:

give me a recipe with ${ingredient_one} and ${ingredient_two}
i want a ${meal} recipe with ${ingredient_one}
give me a recipe

where slots are used to gather information from the user such as the type of meal (breakfast, lunch, or dinner) and the ingredients they have.