 A slide, or linear potentiometer, is essentially a rotary potentiometer stretched out. Both output variable resistance, but instead of detecting a rotational position, a slide pot detects a position along a line. Slide pots are best known for their use controlling audio levels in mixing consoles. Which makes sense. Compared to a rotary pot and knob, it's easier to reference a fader's position with a quick glance. And far easier to operate multiple controls with one hand. Sliders are available in a variety of different lengths, from mini to full console luxury size. Due to their elongated shape and variations between manufacturers, slider pinouts can differ a bit, so be sure to check the datasheet before wiring one up.