Truffle provides a system for managing the compilation and deployment artifacts for each network. To make an actual transaction and put a smart contract on-chain we have to provide Truffle with an appropriate configuration. We configure each network separately. From this post, you will learn how to prepare a setup and deploy to a few widely used test networks.
Depends on how you count, second and third generation blockchain applications are not bound by restrictions of underlying protocols. Programmers can create smart contracts, distributed applications with access to code-controlled accounts - opposed to a private key. Use cases go far beyond exchanging value and applies where users benefit from replacing trust between parties with code.