The Web Content Accessibility Guidelines, or WCAG, are the standard most accessibility laws and procurement rules point to. Version 2.2 builds on the earlier versions rather than replacing them, so a site that met 2.1 is most of the way there.
The new checks focus on people using touch screens, keyboards and screen readers. Buttons and links need to be big enough to tap, focused items must not be hidden behind sticky headers, and anything that can be dragged needs a simpler alternative.
You do not need to read the guidelines to improve things. Try using your own site with only a keyboard, zoom the page to 200%, and check that your text has enough contrast against its background. If something is hard for you, it is harder for someone with a disability.