How does NiceHash work?

Can you explain to me in simple terms how NiceHash operates? I'm particularly interested in understanding the role it plays in the cryptocurrency market and how it connects miners with buyers. Additionally, I'd like to know about the platform's security measures and how it ensures fair transactions between parties. Is there a specific algorithm or methodology that NiceHash employs to match miners with the most profitable tasks? Lastly, could you provide an overview of the fees associated with using the platform and any potential risks that users should be aware of?