Exchanges are where you buy and sell cryptocurrencies, so theyre an integral part of the market. But no two are alike, and its worth doing your research before picking one.
For Popular Bitcoin Exchanges you may visit
https://en.bitcoin.it/wiki/Comparison_of_exchangesI would also highly recommend the bitcoin wiki for all Bitcoin related information. It is objective and well researched. As you can see yourself on the list there, as you can see, has only a handful having actual reviews, with the highest review being 3 out of 10 (those with no reviews must have min 10 user reviews to appear).
I see Bisq there which is I hear very good but surprising not to see Localbitcoins (both are p2p).