The operation of a smart contract can be understood as a sequence of states. A user or system sends a transaction; the network executes the requested function; the rules are verified; and if the operation is accepted, the new state is recorded. The network and the execution model define costs and limits for this process.
Public, private and administrative functions must have explicit permissions. It is also common to log events so applications and monitoring tools can track what happened without having to read the contract's entire internal state.
Smart contracts do not automatically know any real-world facts. When they need prices, documents or external events, they rely on an integration layer. This dependency should be analyzed because it can become a critical point of trust and availability.
In practice, implementation quality depends on the whole set: requirements, architecture, code, tests, key management, monitoring and operations. A well-written contract does not eliminate risks if the surrounding process remains undefined.