SampleNoise
This node is used to retrieve a previously computed and cached random value within a 64x64x64 cubed space using the supplied coordinate vector. When specifying values, you can supply a Node Input, or add fixed values to the node input boxes, or you can add them through the Inspector window:
The inspector also permits you to choose what kind of noise you wish to sample from, which can be either one of the following:
Noise Type  Description 

Perlin 
See here for more information. 
Simplex 
See here for more information. IMPORTANT! This noise type is currently not implemented and will be included in a future udpate. 
Node Input
The SampleNoise node permits the following input:

Coordinate
This input requires a 3 value vector (X, Y, Z) that defines the coordinates within the sample. Input vector values are floats and will be floored to the nearest integer to compute the output result. If the given coordinates fall outside of the cubed space then they will "wrap", so a valid output is always generated.
Note that the cubed space is 64x64x64 in size, and that input coordinates are "wrapped" so it is impossible to sample outside of this precomputed sample space.
Node Output
The node will output a scalar (float) value, which will be a value between 0 and 1.