Schiphol is the largest en most important airport of the Netherlands. Schiphol airport is easy to access by car or by train. The train station is located right underneath the Arrivals Hall.
Besides Schiphol airport there are a few regional airports, like Eindhoven, Groningen, Maastricht, Rotterdam, The Hague, Enschede en Lelystad. So Rotterdam and The Hague are easy to access via Rotterdam The Hague Airport.