The bridge of a ship is an area or room where the ship's navigational controls and other essential equipment related to ship operations are housed and operated. It is so called because it once was a bridge between paddlewheel housings on either side of early steamboats. This new vantage point was deemed so convenient that it was retained after the paddlewheels were superseded.
The bridge is especially useful when the ship is to be brought against a dock as it will usually extend out far enough so that the entire side of the ship may be viewed. The pilot house was initially only a small shelter on an otherwise open bridge, but modern ships will typically extend the pilot house across most or all of the span of the bridge and so the two terms are in practice now interchangeable.