The new value 'anywhere' allows an otherwise unbreakable sequence of characters to be broken at an arbitrary point if there are no otherwise-acceptable break points in a line. Additionally, soft wrap opportunities introduced by 'anywhere' are considered when calculating min-content intrinsic sizes.
This feature address a long standing web compatibility issue related to the 'word-break: break-word' feature. The CSS Text 3 spec still allows the 'break-word' value to ensure compatibility (Safari and Chrome support it), but its marked as deprecated; that's why Firefox doesn't implement it. The 'word-break: break-word' feature provides a behavior that web authors really appreciate, which consist on breaking opportunities account for the min-content size. Several approaches have been explored, but all of them lead to serious web compatibility issues, so that the CSS WG resolved that a new CSS value should be the best solution.
Docs: https://drafts.csswg.org/css-text-3/#valdef-overflow-wrap-anywhere
Samples: https://developer.mozilla.org/en-US/docs/Web/CSS/overflow-wrap https://www.cjcid.com/articles/wrapping-long-words-css-html/
Explainers: https://github.com/w3c/csswg-drafts/issues/2682