Check out the graph below. We see that (3,0) is a root or x intercept. More specifically, the graph only touches the x axis at this point, rather than cross over (in contrast to a root like (-2,0) ). We say that the root here is of multiplicity 2. The multiplicity is due to the exponent of 2 over the (x-3) factor.
You can also say that the graph is decreasing on the left side of (3,0) and then it bounces off the root x = 3 to increase afterward. In this region, the graph never goes below the x axis.