linear-gradient(angle, color1, color2) transitions along a straight direction. radial-gradient(circle at position, color1, color2) spreads outward from a point in a circle. conic-gradient(from angle, color1, color2, …) sweeps colors around a rotation, like a clock hand — which is exactly why it's the tool for drawing a color wheel or a pie chart.
All three accept position stops (%) for each color, and prefixing repeating- turns any of them into an infinitely repeating pattern — stripes, or a target/bullseye.
They're a common way to make a background feel alive, but if text sits on top, check contrast at every point along it — white text quietly disappears into the bright stretch of a gradient more often than teams expect.
When to use
Use linear when you need directionality, radial for spotlights and button glows, conic for pie charts and color wheels.