Hey Rajesh,

Well, actually there are 3 terms related to the seat allocation process in JOSAA(Joint Seat Allocation Authority). They are as follows:

Freeze means you have been allotted a seat and you’ve accepted it and you don't wanna participate in the further rounds of counselling. The counselling process for this category of students will end up here, they only need to report to the allotted institute for confirming the admission.

Float means you have been allotted a seat and you’ve accepted the seat but you want a better programme(quite obvious) than what you’ve been allotted. In this case once you are allotted a seat in the further rounds, you’ll lose  the seat which was allotted previously. And the choices considered for float will be the ones which are above the allotted programme in your filled choices list. So it’s very important to fill choices intelligently. Focus on only those programmes which you want.

slide It again means you’ve been allotted a seat and you’ve accepted it but you seek for a different course in the same institute in which the previous programme was allotted. So its almost equal to float option except the fact that you will be going for choices related to the same institute.