Argent X is a web browser extension and a first wallet for StarkNet, currently running on StarkNet Alpha on the Ethereum mainnet. It's a developer tool, for now, and shouldn't be confused with our Argent mobile wallet.
Argent X is a Chrome extension that helps you create and manage accounts, and connects these accounts to decentralized applications built on StarkNet. It also secures the private keys that can authorize transactions on these accounts.