A Dialogflow context allows you to

a) manage the state of the conversation

b) reduce the list of intents which can fire at any given point in the conversation

You can add input and output contexts to every intent in Dialogflow ES.

How to build your Dialogflow bot in under a week

If it takes you more than a week to build the first version of your Dialogflow bot, then you are probably not following a good process. 

Here I describe some ideas on how you can speed up your bot development. This will be especially useful for you if you are not a programmer.