Oversampling
Temporarily working at a higher sample rate than the final output, so aliasing products land somewhere they can be filtered away.
Anything above the Nyquist frequency folds back down as phantom tones. Nonlinear effects — saturation, distortion, an aggressive limiter — generate harmonics far above the audible range, and at 44.1 kHz they have nowhere to go. A plugin running at 4× or 8× internally lets those harmonics land above the audible band, filters them out and downsamples again. The bill comes in CPU cycles and a little latency.
The trick predates plugins. Philips's first CD players in 1982 paired 4× oversampling with 14-bit converters, because a digital filter was cheaper and kinder to phase than a steep analogue one. Today the idea is taken to its extreme in delta-sigma converters, which sample at several megahertz.