Synchronous operations are those that happen in sequence, where each operation is initiated only after the previous operation has completed. In programming, synchronous code is executed sequentially from top-to-bottom, blocking further execution until each line has been completed.
In a synchronous communication system, for example, a message sender waits for the recipient to be ready to receive the message before sending it. If the recipient is not ready, the sender must wait.
This is contrasted with asynchronous operations, which allow operations to occur without waiting for other operations to complete. Synchronous operations are simple to understand and debug, but can become inefficient if one operation is waiting on another to complete.