How does Parcl work?

Could you explain to me in detail how Parcl functions? I'm particularly interested in how it facilitates transactions between buyers and sellers, and the role it plays in ensuring security and trust during these exchanges. Additionally, I'd like to know if there are any fees associated with using Parcl's services, and if so, how they are calculated. Understanding the overall mechanics of Parcl would be incredibly helpful in determining whether it's a viable option for my needs.