Try to do more research on your own and you will understand it better. You can research on lens compatibility if you are looking into old lenses. The D3100 and D3200 have limitations with many older lenses
AiS lenses are manual focus lenses by design.
On entry-level Nikons, there is also no metering capability with these lenses if I remember correctly. this means you will only be able to use Manual Exposure (M) mode and even then you won't have the exposure meter to guide you.