WalletConnect is an open-source protocol to connect between dApps and mobile wallets. A user can simply scan a QR code on the web app and manage funds from their mobile. This makes wallet connect a protocol for both dApps and wallets.
Have you ever used WhatsApp web? You scan a QR code and instantly use WhatsApp on your browser. Let's say Wallet connect is the QR code service for Ethereum wallets.
WalletConnect will convert a mobile wallet to Meta Mask or Binance Chain wallet. You can sign and verify transactions from your mobile that are initiated on a web app.
The protocol establishes a remote connection between two apps or devices. The session is started by scanning a QR code (desktop) or by clicking an application deep link on mobile. Communication happens over a bridge server that relays messages without exposing data.
Wallet connect does not charge any fee. There is no token or blockchain association of any kind. The source code is available on GitHub. There is extensive documentation for developers and deep analysis.
There are dozens of supported wallets. The most popular are Trust, Metamask, Atomic wallet. These wallets support and need wallet connect to provide users access to the Ethereum world.
There are also a huge and popular number of platforms that have integrated WalletConnect. OpenSea is one of the most popular platforms these days.