The Raiden Network is an infrastructure layer on top of the Ethereum blockchain. While the basic idea is simple, the underlying protocol is quite complex and the implementation non-trivial. Nonetheless the technicalities can be abstracted away, such that developers can interface with a rather simple API to build scalable decentralized applications based on the Raiden.
Raiden Network 101
Blockchains don’t scale well because there needs to be global consensus on the order and outcome of all transfers. Every participant needs to learn about all updates to the shared ledger. Hardware and bandwidth constraints set a limit on the number of updates per second that can be shared in a decentralized network. The basic idea of the Raiden Network is to avoid the blockchain consensus bottleneck. This is done by leveraging a network of payment channels which allow to securely transfer value off-chain, i.e without involving the blockchain for every transfer.