The Stellar Lab is a set of tools that enables people to try out and learn about the Stellar network. The Lab can build transactions, sign them, and submit them to the network. It can also make requests to RPC and Horizon endpoints. You can save your transactions and runbooks for future use.
For Stellar docs, take a look at the Stellar developers site.
Learn to build world-class applications on the Stellar network in a gamified experience
Tools, like the Stellar CLI, for reading and interacting with smart contracts on the Stellar Network
Learn about Stellar RPC, a gateway to the Stellar network
Learn about Horizon, the REST API for interacting with the Stellar network