A concourse, generally speaking, is an area where pathways or roads converge. According to Merriam-Webster, a concourse can also be “an open space or hall (as in a railroad terminal) where crowds gather.”
At the airport, a concourse is usually the area(s) in an airline terminal where the gates are located.
Source 1: “Concourse.” Merriam-Webster.com. Merriam-Webster, n.d. Web. 26 Mar. 2017.