Unlike loops (which repeat), one-shots are individual sounds: a single kick drum hit, a single snare crack, a single chord stab, or a single vocal phrase. Producers load them into samplers or DAWs and trigger them to build patterns.
One-shots give producers maximum control. Instead of using a pre-made drum loop, you can build your own pattern from individual kick, snare, and hi-hat one-shots — choosing the exact sounds you want.
Drum kits sold online are typically collections of one-shot samples organized by type: kicks, snares, hi-hats, claps, percussion.