This is the Changi Airport MRT Station (CG2) which is part of the Changi Airport Extension of the East-West Line and is situated on Airport Boulevard. The station is located underground and links to the basements of Terminal 2 and Terminal 3.
The Changi Airport Extension is part of the East-West Line, a mass rapid transit rail system managed by SMRT Corporation, one of two major bus/rail transportation companies in Singapore.