Fairway woods consist of 3, 4, 5, 7, and even a 9 to provide you with a different degrees of loft. The fairway wood was designed to produce a range of long shots at various height and lengths.
The 3 wood gives the longest shot because of the loft and is typically the hardest to use. It is more common for a golfer to use a 4 or 5 wood in the fairway than a 3 wood. 3 woods are more commonly used in place of a driver off the tee box. The 7 wood is even easier to hit and provide much more loft on your shot but won't carry as long.
The shaft of woods are much longer than that of irons so your stance needs to be adjusted and your swing needs to be flatter. The sole of a wood is also different than an iron. Instead of cutting through the grass like an iron, the driver is designed to bounce off the ground. When you use a fairway wood, it is important to sit the club absolutely flat to the ground to take advantage of the bouncing. If you wrongly push your hands forward in your swing ahead of the club head, the back edge of the club will rise and lose the forgiving effect of a wood.