For any musician their instrument is their baby, whether its a guitar, cello, violin, banjo or something else. These prized instruments need to be protected from the elements as well as any potential damage caused during transport, so that they can continue to make fine music for many years to come. For most people an entry level model would be considered disposable, but a vintage instrument, made using rare woods and with their wonderful tone can be worth in excess of thousands of dollars, and they really need the type of protection offered by a hard case.
Hard cases are made by various manufacturers using an array of materials in an effort to try and balance out such factors as ease of use, weight, cost and insulation. On a flight case you will find that they use heavy plywood, with the edges and corners protected by strong heavy metal, as well as the latches, this will help protect against the damage often caused by airlines. The interior of the case will be lined with custom cut foam to help isolate the instrument and protect from shocks and impacts that can damage some instruments.
Heavy reinforced plastics and rubber compounds can be used on some models of flight case. Azdel, which in the past was used to make hockey pucks, has been used in some guitar cases in recent times. There are some advantages to using these materials over wood, such as lighter weights and water resistance, but of they become damaged they are harder to replace that wood.
For a more modest budget there will be many plastic and wooden guitar cases available at most outlets. These are going to offer your instrument some basic protection from the elements and from being damaged by other objects. This type of case is normally covered in velour on the outside, and shaped foam on the inside, taking the rough form of the instrument, and secured using a small latch and lock.