Time bombs were generally miniature seismic charges that detonated after about five (or ten) seconds after activation. They were used by pilots to destroy the major systems of capital ships from the inside, as well as by infantry for other sabotage purposes. Bothan spies also used time bombs. Time bombs were also used by Wookiee smugglers to destroy gun posts and light Vehicles. The first manufacturers are unknown, though rumor had it that the inhabitants of Mon Calamari were the first designers.
Some time bombs were also improvised. A notable example are TIE/LN starfighters, where misaligning an energizer for its eponymous engines even slightly will have them turn into improvised time bombs.