Muon is a chain-independent and stateless DON (Decentralized Oracle Network) that enables dApps to make their off-chain components decentralized.
A Testnet (ALICE) and two mainnets (Pion and Muon) form the ecosystem. See the details of Muon Ecosystem. ALICE and Pion are currently up and running.
By incorporating Muon, the manner in which decentralized applications store, process, and access data will be fundamentally transformed. This means when a dApp integrates with Muon, Muon/Pion network takes care of the complicated calculations that a smart contract cannot perform. In simple words, it is like the CPU and RAM of a PC.