Final answer:
A fault or a bug is when a system deviates from its specified behavior and can lead to failure. Debugging is the process of checking for these deviations and fixing them.
Step-by-step explanation:
A fault or a bug refers to a deviation of observed behavior from specified behavior. It is when a system does not behave as expected or specified. This can be due to a mechanical or algorithmic cause, and if the system continues to process in this state, it can lead to failure.
For example, in computer programming, a bug may cause a program to crash or produce incorrect outputs. To identify faults or bugs, a process known as debugging is used, which involves checking for deviations between the system's observed behavior and its specification.