The commonly-used Galaxy Classification indicates a Galaxy's morphology, i.e., shape. Edwin Hubble developed the basic classification still used, known as the Hubble Sequence:
More recent developments, generally indicated by a suffix or prefix, add more detail, often distinguishing galaxies formerly classified as "irregular". For example, the classification "SBm" is based upon the Large Magellanic Cloud (LMC)'s form, which does have characteristics associated with the classic barred spiral. In the less-developed system, the LMC falls under "irregular".
Large Magellanic Cloud (LMC)
Small Magellanic Cloud (SMC)
Ursa Major II Dwarf