Originally published in 2008, the underlying essence of a structure elucidation process is to structurally distinguish an unknown from a set of possible isomers. This is evident by the number of possible isomers for a given molecular formula.
The chart below divides isomers into three groups: Structural/Constitutional/Regio, Spin and Stereo/Spatial isomers. Wikipedia links are included for further reading into the different isomer classifications.
Note: some of the classifications may overlap.