In US English, a walkway is a composite or umbrella term for all engineered surfaces or structures which support the use of trails. These include sidewalks, footbridges, stiles, stairs, ramps, paseos or tunnels. Walkways can also be used by passengers to board or disembark from an aircraft to the terminal building.
In UK English, walkway more specifically means a covered or raised passage in a building or a wide walk in a park or garden.
A walkway can be at ground level, elevated, such as a boardwalk, or floating. It can be a simple paved path or something more complex to cross a road or a body of water. An open pedestrian overpass or a special tunnel are also examples of walkways.