There are two main types of wood. There is hard and soft. Hard wood is the better choice for a long lasting fire. It is denser and therefore burns slower. This means less wood is needed, and the fire doesn't need to be tended as often.
Even though soft wood is not the best option for a fire, it can be useful. Hard dense wood will give off a nice flame, but it does not light well. Soft wood is more porous and normally has some form of resin inside. These two factors make it ideal for lighting a fire more quickly. It is the best choice for starting a fire, but should not be used as the constant fuel source. Soft wood burns quickly and the fire would have to be tended too often.
Good Hard Woods for a Fire
Even if hard wood is the best for a fire, there are still some woods that are better than others. Ash, Douglas fir, Hickory, oak and holly are all good hardwoods for burning. Ash and holly will burn even if they are green, and all burn slow at a high heat. Oak is the most difficult of these because it needs to season a long time in order to burn well like the others. Seasoning is when the wood is allowed to dry. Oak is best if seasoned for a couple of years. Otherwise it tends to give off an unpleasant odor.