Overview of Haveno
Haveno is a platform where people meet to exchange Monero for other cryptocurrencies or fiat currencies. Monero coins are used as security deposit by traders, which will then make the exchange outside Haveno (for example a bank transfer from trader A to trader B). After the exchange is completed, both traders will receive their security deposit back. One trader will receive the asset (for example, Euros or Dollars) and the other trader the amount of XMR agreed for that asset.
The Haveno Network
When running an Haveno app, you'll be one of the nodes that composes the Haveno network. There is no central entity, trades happen directly between nodes (peers), that's why it's called a peer-to-peer network (P2P). This network runs on Tor, a technology that makes communication between peers private.
Haveno, unlike a centralized exchange, doesn't provide any liquidity to the network, but instead offers a place for people to meet and an escrow system to make sure both parties honour the terms of the trade until it's completed.
Note
Haveno is fully non-custodial: the wallet is created locally and only the user has access to it.