What are tri-state buffers and why are they used?

Tri-state buffers have three output states: logic 0, logic 1, and high-impedance (Hi-Z). When enabled, they pass the input to output; when disabled, the output is electrically disconnected (Hi-Z). They allow multiple devices to share a common bus without conflict by enabling only one driver at a time. Applications include data buses, bidirectional ports, and memory interfaces. Design must ensure no two tri-state outputs drive simultaneously (bus contention) which can damage components and cause unpredictable logic levels.