The link below allows one to download and view the complete Common Data Language (CDL) file specification for Collection 051 and the older Collection 005.
This file spec gives a complete description of the 06_L2 HDF product file, including all the Scientific Data Sets and their local attributes.
MOD06_L2 File Spec [C006] (123 Kb)
MOD06_L2 File Spec [C051] (80 Kb)
MOD06_L2 File Spec [C005] (51 Kb)