This CSS property is thoroughly explained here, with working examples:
This CSS property is incredibly versatile and even beginners will benefit on day one of using Webflow:
Clicking some buttons in Webflow (i.e,. p in a div, used as a button) quickly will cause Webflow to highlight the text. This looks very amateurish on a professional website. See attached image (or click here).
To prevent easy copy-pasting of text (say of sensitive or gated content), this CSS property is usually a strong enough line of defense.
By enabling the user-select: all choice, you can now single click to highlight an entire line. This is very useful for users selecting text to copy, like addresses or phone numbers or URLs.