Lotus is an implementation of the Filecoin Distributed Storage Network. You can run the Lotus software client to join the Filecoin Testnet.
For more details about Filecoin, check out the Filecoin Spec.
Lotus is architected modularly to keep clean API boundaries while using the same process. Installing Lotus will include two separate programs:
The Lotus Storage Miner is intended to be run on the machine that manages a single storage miner instance, and is meant to communicate with the Lotus Node via the websocket JSON-RPC API for all of the chain interaction needs.
This way, a mining operation may easily run a Lotus Storage Miner or many of them, connected to one or many Lotus Node instances.