As i know, there is only Ngoko and Krama (Kromo). But, they still devided into this part based on the politeness speech level.
1. Bahasa Ngoko (Bahasa Kasar - LOW)
a. Ngoko Lugu
b. Ngoko Alus
2. Bahasa Krama (Bahasa Halus - HIGH)
a. Krama Lugu / Krama Madya
b. Krama Andhap
c. Krama Inggil
But as Javanese itself, i still dunno what's the difference between them. The only thing i know is, Ngoko as an Informal speech is used between friends ,close relatives, and the older to younger one. And it has been used in East Java - i.e. Surabaya, Malang, etc. Then, the Krama language as the most polite way to talk to in Javanese recently used in West Java area, such as Yogyakarta, Solo, Semarang, etc. Hope it's useful XD.
And don't forget to spell this "a" as "o" in Javanese. LOL :))