KYC is an abbreviation for ‘know your customer’. The term is used for exchange providers who (partly) have to be able to justify who and what customers buy and sell their products according to the regulations. With regard to crypto, which is mostly decentralized and unregulated, the government wants to prevent and counter money laundering and people avoiding tax payments. With the KYC policy, active investors are less transparent and will be tracked down more quickly if they try to launder money. The ‘knowing’ happens when an ID (driver licence or passport etc.) is provided when a customer signs up at an exchange or a broker. In the Netherlands the KYC policy falls under the ‘Wet ter voorkoming van witwassen en financieren van terrorisme’ translated to ‘Law on the prevention of money laundering and financing terrorism’ or the Wwft. Read more here (Dutch).