The scope of employment of a person refers to all the duties they're tasked with performing in the course of their job. By default, this includes all the activities outlined in that person's working contract, though the broad and flexible definition of the term can lead to many additional tasks being flagged as falling under one's scope of employment. For example, a repairman's default scope of employment includes all of the duties that repairman serves, such as maintenance and repair work.
However, any extra activities which have been requested by the employer can also fall in one's scope of employment - for example, running extra errands unrelated to repair work in the case of the repairman above. Furthermore, if an employee performs some action while on duty, that action will almost always be flagged as falling in their scope of employment.
The purpose of defining a scope of employment is to make it easier to settle legal disputes related to a person's activities. Usually, when malpractice is committed, the legal outcome can be greatly affected by whether or not the action was in that person's scope of employment. The fact that any activities ordered by the employer can be considered part of one's scope of employment has lead to some controversy because of this, and it's not uncommon for employees to find themselves in legal trouble due to orders issued by their superiors.