TON is blockchain of blockchains with a masterchain to rule them all.
You can learn more about general architecture in Basic Concepts section.
Learn more on how to build with TON.
Standard smart contracts is the best way to study how FunC works.
Whitepapers overview provide more details on the original vision Dr. Nikolai Durov had when he developed the concept.
TON can't work without payments, testnet and nodes required to be the backbone for functioning blockchain.