Stones do not come with perfectly flat surfaces for easy construction and a good looking veneer, so any flat surfaces must be manufactured out of the available rock. Masons began dressing stone many centuries ago from local rocks, and enterprising rock masons built quarries that eventually began cutting and selling stones to be used for building. Older buildings and often have more texture to them, and it is because older techniques did not always provide a completely flat surface.
Hammers were often used to break off pieces of the rock that stuck out too far, and it is now thought of as a primitive method of dressing the stone. While it does help to even out a wall or rock face being built, it can still leave uneven surfaces. Modern stonework that requires a textured look might use this method, but chisels are generally used to give a finer surface that retains its character.
Craftsmen are still trained in these ancient techniques today, but they also use more modern methods to get the look they want. Power tools have been added to help them get the look they want, and they come in a range of sizes. Jackhammers can be used for large stones that require a rough look, but power saws are best for a smooth surface.
Stone masons in former centuries had only chisels and hammers to break off unwanted rock faces, but modern technology has added more tools to their arsenals. Dynamite is often used to create rocks in quarries, and it is generally cut with water saws. It might seem an easy solution now, but it took time to develop this technique. Cutting rock faces creates a great deal of heat, and the water keeps the rock cool enough that a precise cut can be made.