Using stone and rocks in your landscaping gives the area another interesting element. This is called hardscaping, using a material other than living plants. The term rock is much bigger than a stone which is smoother due to weathering.
I have used a large piece of petrified rock as an anchored center to the flowerbed which surrounds it. The use of rocks as a rock bed with native grasses cuts down on the water. Also if weeds come through, use can spray with a 2-4, D which will not harm the grasses.
Different colored stones can be used in planting beds on perennial and shrub areas. The colors separate the areas for a better focal point.
A stone pathway will be attractive and a way of keeping your shoes clean coming in from the garden. Adding different colors of stone provides more interest. You can even use stones landscaping a dry creekbed.
If you can get your hands on a large “field” stone, use it to change a dull area in your back or front yard.
Using rocks as a mulch around trees and borders will not wash or blow away in storms, so lowers the maintenance which in turn lowers the cost over time.