Good afternoon, answer me please. What is the side chain ?? It is possible in detail

Hello, this is the block that is separated from the parent. But attached with a two-way binding.
Well, what does it give? Please explain to the newcomer as clearly as possible

As I understand it gives the assets the opportunity to be interchangeable. And just as easy to navigate the chain
All right, so it really is.
This means that each side chain has its own data sets that function independently of the parent chain.
Only the test network will live and have a monetary value inside it. If this happens, as planned, the ETC and CLO smart contracts will be interchangeable. This is a very important material, but it still remains to be seen.
I somewhere heard that there is another problem about cold steakings. With which ETC has already faced.