A General Sales Agent (also known by its acronym, GSA or General Sales Agent) is the sales representative of an airline in a specific region or country.
Typically the GSA is responsible for selling all of the airline's products in that region which includes flight tickets and cargo space. A GSA will normally sell the product of more than one airline.
Airlines often use GSAs in areas in or from which they do not operate, allowing them to have a presence when selling in a country at a lower cost than opening their own commercial office in the short term. It can even employ its services since the GSA figure has historical links with travel and cargo agents which are too costly in terms of time for the airline to develop.