Context & Knowledge
In Dialogflow each intent takes (multiple) intent contexts and sets output contexts when finished. Only the intents that meet the current context are being triggered.
Context
To follow up on previous answers or to stay within a topic that the agent is talking about we can use context. That makes the agent more aware of the situation.
Entities
These can be words or short phrases that the agent can catch from user input. In Dialogflow we can store these values and pick them up anytime later in the dialog.