To understand surds we have to understand powers and there uses. So to start we should look at powers such as what is 22 , 32, and 52. This shows us going up but then we look at how we square root things after this so how do you √4 and then √9 and √25. We do this to see how powers work up or down. Surds just let us express more complicated numbers more easily. To do this we look at √2 and how we cannot get a whole number out of it; a lot like pi it doesn't have an end. This doesn't mean it isn't useful. √2 is useful a lot especially in trigonometry because of the unit triangle.