For example i transfer my bitcoin to bitrex. It will take mining fee and a huge time ( few hours ) to actually appear in bitrex wallet.
Now from bitrex i can transfer between Bitcoin -> Neo -> Bitcoin -> Eth -> Neo instantly without any mining fee.
How it actually does that ?
Here what i think:
After i transfer them my bitcoin to my online bitrex wallet, they transfer it to their own secret GLOBAL wallet of that coin. Then we just do exchange on their database not in real. Then when withdrawal they transfer it from their GLOBAL Neo wallet -> my online neo wallet -> my offline neo wallet.
Thats just my thought i know its wrong but i need someone to explain me that.