What is the difference between the different brands of Jet (e.g. JetLite, JetKonnect, plain-Jet and so on)?

well jet airways is the main carrier, they are the full service carrier. They fly all the international destinations and domestic flights too. They then bought Air Sahara which was the only other private carrier at the time. They kept this as a low cost carrier, and renamed it Jet lite, flying to the same places and restructuring parts of the network. Then due to the economic downturn, where low cost carriers were doing better, so Jet Airways' market share was decreasing. Therefore Jet airways then created another low cost carrier, Jet Konnect, which operated under the same code (9W). This allowed people to connect from international flights to cheap domestic flights.

Jet Airways - International and Domestic
Domestic seating: Business and Economy

Jet Konnect (no frills)- Domestic
Domestic seating: Economy or Economy and cheaper Business class on some flights. No frills therefore need to purchase own food.

Jet Lite - Low cost arm, flies domestic mostly and one or two international destinations.
Domestic seating: Economy

Thanks very much for the detailed explanation.

So reading the above, do I understand correct that in JetLite I do NOT have to pay for food, whereas in JetKonnect I do (like all other LCCs)?

What happens if I am flying on a Business Fare on JetKonnect - do I still have to pay for food?

Not true. Jetlite - you will need to pay, same as in Jet Konnect. It is only the full service 9W flights that you don't pay for food (these flights are easily identified by 3 digit flight numbers - ignore the leading "0", as opposed to 4 digits for all the rest).

Technically, this is a separate class of service, called Jet Konnect "Select". No payment for food, but you get what you'd normally get in economy of a full service flight.

you don't have to pay for food & you will get business class seats....but its not exactly like a normal business experience....

Very true. In fact, the only thing that's business class-y, is the seat.