There are a total of 20 IIMs in India. They are generally classified into Old, New and Baby IIMs. They are in order of the year they started operations.
IIM Shillong (Recently added to the old IIM list)
New IIMs (Started batches in 2010, 2011)
Baby IIMs ( Started batches in 2015)
IIM Jammu (Started a year later than the above 6)