Traditional color wheels usually rotate hue in HSL or HSV. That is easy to teach, but it does not match how people see brightness. The same HSL lightness value can produce a bright yellow, a heavy blue, and a red that sits somewhere between them. A harmony based on that math can look uneven even when the angles are correct.
OKLCH separates perceptual lightness, chroma, and hue. This tool keeps the base color's lightness and chroma as stable as the sRGB gamut allows, then rotates hue. When a rotated color would clip outside displayable sRGB, the tool reduces chroma along the same hue rather than shifting the relationship.
That approach is especially useful for monochromatic and triadic palettes. Your output still needs design judgment, contrast checks, and likely tonal scales, but the first draft is closer to how a human reviewer expects the colors to feel.