The word agent, in the realm of IT, can have multiple meanings.
In the area of systems management, an agent is a user, who has assumed the role of an agent for the sake of the completion of a particular task. There are many kinds of tasks that need to be accomplished in the world fo systems management, and there are certain users, who specialise in certain kinds of tasks. In order to get the best possible outcome, the user who is an expert at a certain task is assigned the role of ‘agent’ until the task is completed.
The other explanation of an agent, is an entity that represents managed object, by either, issuing notifications regarding the managed object or handling requests from the managers regarding the management of said object. Essentially, an agent acts as a conduit between the managers and the final task that has to be completed.
Sometimes, an agent is not a person, but rather, a software that performs a task on behalf of the user, within an application.