Fault tolerance refers to the ability of a system or component to continue functioning correctly in the presence of faults or failures, such as hardware failures, software bugs, or other unforeseen issues. A fault-tolerant system is designed to detect, isolate, and recover from faults without experiencing complete failure or downtime.

Fault tolerance is an important concept in system design, particularly in distributed systems or systems that need to operate reliably in challenging environments.

It involves implementing redundancy, error detection, error correction, and error recovery mechanisms to ensure that the system continues to operate even when certain components or subsystems fail.

There are various techniques and strategies for achieving fault tolerance, such as replication, where multiple copies of the same data or service are maintained in different locations, so that if one fails, others can take over; checkpointing, where system states are periodically saved, so that in case of failure, the system can be restored to a previously known good state; and graceful degradation, where the system can continue to operate with reduced functionality in the presence of failures.

Fault tolerance is crucial for ensuring high availability, reliability, and resilience of systems, particularly in mission-critical applications where system failures can have severe consequences.

By incorporating fault tolerance mechanisms in system design, engineers can create robust and dependable systems that can continue to operate and deliver expected results even in the face of unexpected failures.