A monorail is like a train. Trains have two sets of wheels that balance on a railway track, but monorails balance on one rail. Monorails are often transport people around cities. Some monorails and trains use magnets to hover on their rails. They are called maglev trains. This reduces friction between the train and the rail. The first monorail was invented in the 19th century. The monorail has a different wheel system than other trains. Instead of being on the rail, it goes beside the rails. Monorails are usually complicated and expensive, so most places do not have them.