An Agent is a reusable object which forms the building block of a Data Stream. When a number of Agents are connected together, a Data Stream is formed.
Each Agent is designed to perform a specific function in the stream. For example, they can be used to retrieve data from a database in real-time, display data, filter, sort the data, or save the data somewhere else, depending on the function of that individual Agent.
It is recommended that you read the article listed below to improve your understanding of Agents.