Adobe RGB
Adobe RGB is a color space with a wider range than sRGB, especially in the greens and cyans. It's often used for professional print work, because printers can reproduce those colors. For the web it's actually a poor fit, there you use sRGB.
Sending photos to a good print shop, Adobe RGB can deliver richer prints, provided your screen and workflow are set up for it. On the web it often goes wrong: an Adobe RGB file on Instagram looks dull because the platform expects sRGB. So be deliberate: Adobe RGB for print, sRGB for screen. When in doubt, choose sRGB, it's safe everywhere.
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The presets on this site set these adjustments up for you as a starting point, which you then fine-tune to taste.