There are 10s of cryptocurrency exchanges, there are primarily custodial exchange, non-custodial exchanges, decentralised exchanges.
- Custodial - Exchanges like Binance, Coinbase, they store your cryptocurrencies with them, you do not have access to your private key
- Non Custodial Exchanges - Exchanges like Changelly, N. Exchange,ChangeNow, etc. in these exchanges you send coins from your own wallet, and receive coins in another wallet.
- Decentralised Exchanges- IDEX, ether delta, not very easy to use, very bad UI.
I would always use an exchange which do not store my currencies, also I want to always see which exchange is offering me the best rates to trade coins, I want to compare prices at leading exchanges like ShapeShift, Changelly, Changer, ChangeNow, Binance, Bittrex, Cryptopia, HitBtc etc.
Therefore I use https://coinswitch.co/, CoinSwitch exchange is an aggregator of leading exchanges, and provide the best rates to trade.