The Object Type in Simbad is defined as a hierarchical classification: a numeric type is made of up to four levels corresponding to classes detailed below.
A presentation of the system can be found in the paper by F. Ochsenbein and P. Dubois in 'Astronomy from Large Databases II:' ed. A. Heck & F. Murtagh, 1992, pp 405-410
Note that Simbad emphasizes the physical nature of the object rather than a peculiar emission in some region of the electromagnetic spectrum or the location in peculiar clusters or external galaxies. Therefore objects are classified as peculiar emitters (classes 01. to 07.) only if nothing more about the nature of the object is known, i.e. it cannot be decided whether the object is a star, a multiple system, a nebula or a galaxy.
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Each class has normally a standard designation, a condensed one (used in tables) and an extended explanation.
Please see list of otypes : here