Context is like a session, where previous session information is maintained so that the next context can have access to that session information. For example, upon meeting a stranger in a bar, you initiate a conversation, asking the name of the person you are speaking with. From that point on, you know his or her name and you might use his or her name during the conversation. Another example is during a conversation, where you are asked the ambiguous question, "When is his birthday?" by a friend, but you do not know who "he" refers to, in which case, you might ask your friend who he or she is referring to. When your friend explains that they are asking about John Doe's birthday, you have successfully established the context that "he" refers to John Doe.
In Dialogflow, contexts can also be used to establish and control conversational flow, allowing only a specific intent to be triggered if specific contextual requirements are met. For example, during the checkout process in an e-commerce store, you only allow the user to buy an item if all the necessary requirements are gathered, such as credit card information and a shipping address.