What is a sequential circuit and how does it differ from combinational?

A sequential circuit has memory elements (flip-flops or latches) and its output depends on both current inputs and previous state (history). Unlike combinational circuits, sequential circuits can produce different outputs for the same input depending on current state. Examples include counters, shift registers, state machines, and memory units. Sequential circuits can be synchronous (clocked) or asynchronous, with synchronous design being preferred for predictable timing behavior.