A matrix work environment is a structure where people or workers have more than one reporting line. Typically, it's a situation where people have more than one boss within the workplace.
Matrix structures are common in big companies that operate in different states or countries. Many companies start with a single operating line that oversees all the activities of the different departments. As a company grows, the functional heads may decide to assign some of the duties to department managers so as to save time on handling issues. A matrix structure functions well for human resources and information technology departments as it allows more coordination and increased integration.