Sphingosin differs from glycerin in that it is not a 1,2,3-triol but a 2-amino-1,3-diol. In addition, sphingosin contains a 15-carbon side chain with a trans double bond.
Sphigosine is the "backbone" of sphinomyelins and cerebrosides. Sphinomyelin is sort of the "phosphatidic acids" analogs in that the terminal alcohol function forms a phosphate ester and the amino group is bound via an amide bond to a fatty acid. Cerebrosides are ether (at terminal OH group with alcohol function of a sugar) and amide (at C2-amino group) derivatives of sphinosine.