Agent

Let's start with the definition of agent. Based on Merriam-Webster, an agent is:

a computer application designed to automate certain tasks (such as gathering information online)

The goal of an agent is to finish some tasks.

There are two types of agents: conversational agents and task execution agents.

Conversational Agent

A conversational agent presents a chat-bot like UI to end users. It usually provides multi-modal input and output, including text, image, audio, and video.

Task Execution Agent

A task execution agent finishes a particular task when it's executed.