Dialog flow: basic

The process a Dialogflow agent follows from invocation to fulfillment is similar to someone answering a question, with some liberties taken of course. In the example scenario below, the same question is being asked, but we compare the "human to human" interaction with a conversation with an Dialogflow agent.

Welcome	Invocation
Bill's friend Harry wants to ask him a question. So as not to be rude, Harry says "Hello" to Bill first.	In order to start a conversation with an agent, the user needs to invoke the agent. A user does this by asking to speak with the agent in a manner specified by the agent's developer.
Request	Intent
Harry asks Bill "What's the weather supposed to be like in San Francisco tomorrow?" Because Bill is familiar with the city and the concept of weather, he knows what Harry is asking for.	A user asks the agent "What's the weather supposed to be like in San Francisco tomorrow?" In Dialogflow, an intent houses elements and logic to parse information from the user and answer their requests.
...	User Says
	For the agent to understand the question, it needs examples of how the same question can be asked in different ways. Developers add these permutations to the User Says section of the intent. The more variations added to the intent, the better the agent will comprehend the user.
...	Entities
	The Dialogflow agent needs to know what information is useful for answering the user's request. These pieces of data are called entities. Entities like time, date, and numbers are covered by system entities. Other entities, like weather conditions or seasonal clothing, need to be defined by the developer so they can be recognized as an important part of the question.
Fulfillment	Fulfillment Request
Armed with the information Bill needs, he searches for the answer using his favorite weather provider. He enters the location and time to get the results he needs.	Dialogflow sends this information to your webhook, which subsequently fetches the data needed (per your development). Your webhook parses that data, determines how it would like to respond, and sends it back to Dialogflow
Response	Response
After scanning the page for the relevant info, Bill tells Harry "It looks like it's going to be 65 and overcast tomorrow."	With the formatted reply "in hand", Dialogflow delivers the response to your user. "It looks like it's going to be 65 and overcast tomorrow."
Context	Context
Now that the conversation is on the topic of weather, Bill won't be thrown off if Harry asks "How about the day after that?" Because Harry had asked about San Francisco, follow up questions will more than likely be about the same city, unless Harry specifies a new one.	Similar to Bill's scenario, context can be used to keep parameter values, from one intent to another. Contexts are also used to repair a conversation that has been broken by a user or system error, as well as branch conversations to different intents, depending on the user's response.