mine have the have 24input jacks and 6 output jacks.

basically what is the output jacks are for?

does the output jacks be useful for recording studio?

Snake cables should have the same number of jacks on each end. They are used just as any other cable, just used to run several cables over a longer distance without getting all tangled and messy. I have a 10' snake with 1/4 inch male jacks on one end and male RCA jacks on the other to run from my mic preamps to my recording device. Studios use them often to plug microphones into a box on the wall and run the cables under the floor or through the wall into the console or preamps. Same in live sound. Use them when you have lots of things in one spot that you need to plug into gear in another spot.