QUICK ANSWER
Deadbeat Seconds is a mechanical complication where the seconds hand jumps precisely once per second, similar to quartz movements.

Deadbeat seconds (also called jumping seconds or true seconds) make the seconds hand jump in precise one-second increments like a quartz watch, rather than sweeping smoothly. This mechanical complication uses a secondary escapement to release energy at exact one-second intervals, showcasing exceptional craftsmanship.
While both display tick-by-tick seconds movement, deadbeat seconds use purely mechanical complications with springs and escapements, not electronics. The mechanical version is far more complex and expensive to produce, making it a prestigious complication. Quartz achieves it simply through electronic oscillation.
Not necessarily. The complication itself doesn't improve overall accuracy—it's primarily an aesthetic and technical showcase. However, watches featuring deadbeat seconds are typically high-end pieces with excellent base movements, so they tend to be very accurate due to overall superior construction and regulation.

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