Timber comes in various grades, various appearances and many different shades. You will generally use different kinds of timber for different purposes – for example, you wouldn’t choose premium timber for covering the floor of an outbuilding, but you might use it for a floor covering inside of a home. There can be a great deal of variation in terms of price, even if you have a more premium type of timber like oak.
Whilst there are differences in terms of quality, much of your decision will come down to personal preference. You might choose a lower quality of wood if you are looking for a more rustic appearance, for example, if you are applying cladding to an exterior building. In this instance, it is far more acceptable to have a rustic look and a type of timber has knots and shows the woodgrain up clearly. Get some timber samples and see which ones appeal to you.