Centralized cryptocurrency exchanges or a CEX for short, are online platforms used to buy / sell cryptocurrencies and fiat currencies. Approximately 99% of all crypto transactions go through centralized exchanges. They are used to exchange fiat currency (e.g. USD, NZD) for crypto and are the most common means that investors use to buy and sell cryptocurrency holdings. Centralized exchanges are operated and controlled by a company, which means the company controls your wallet. Most people therefore transfer their crypto holdings out to wallets that they control like their Metamask wallets or to a hardware wallet. Examples of centralised exchanges are Binance, CEX and Crypto.com.