Noise Modifier
The noise modifier distorts a 3D mesh and uses a Seed to determine the distortion profile. Scale is used to determine how big the effect should be across the whole object, a smaller scale results in a more distorted surface, useful for making simple terrain especially when using Fractal. Fractal makes the surface rougher and is good for creating a simple mountainous landscape.
Axis strength determines the amplitude of the effect on what ever axis you choose, in the below example only the Z axis is being effect to create a type of hilly terrain.
Noise is good for several effects. The most obvious is that it can be used to quickly generate a landscape, although the over all quality of will be determined by how many subdivisions your mesh has. The above plane is 128 by 128 subdivisions.
The noise modifier can also be used as a simple fluid effect for things like an ocean or a piece of cloth blowing in the wind. This is achieved by setting and changing the noise Frequency and/or Phase throughout the timeline.