Out-and-back hikes are when a person hikes to a destination on a trail, and then returns to their starting point on the same trail. This is the most common form as hiking as it requires little planning, and many times is the only possible way to reach a hiking destination. The advantages of this type is that the hiker will have a lesser chance of getting lost, and will know what to expect on the way back from their destination. The downside is they will see the same terrain twice, albeit from a different angle, on the return.
