Gamut
Gamut is the full range of colors a device or color space can show. A vivid green or deep orange might fall within your screen's gamut but outside your printer's. Colors that fall outside get 'clamped' on display to the nearest achievable color.
When editing, you can accidentally create colors that are too saturated for your purpose, for instance for print. Soft proofing shows in advance which colors fall outside the gamut, so you can pull them back before printing. A gamut warning in Lightroom or Photoshop lights up those areas. Keep in mind that web (sRGB) has a smaller gamut than many printers in the cyans and greens.
Related terms
Prefer a look in one click?
The presets on this site set these adjustments up for you as a starting point, which you then fine-tune to taste.