dude, you used the tag 'bitshares' here however you obviously haven't been over to check it out. If you want, check out on Google why DEX vs CEX. When you are ready, here is a guide I wrote https://steemit.com/bitshares/@apasia.tech/rough-guide-to-trading-on-bitshares-dex-for-beginners-nov-2017-latest-gui-release-v2-0-171121