Caret-Separated Text (CST) is the parsing syntax used in the uitext directory of The Sims Online.
Each text string is enclosed with carets ("^"s) and is identified by how many other strings preceded it in the file, plus one; that is, the one-based index of that string. Any text which is not enclosed with carets is considered a comment and ignored. Neither strings nor comments may use the caret character.
In The Sims Online, cst files are encoded in UTF-8, as can be seen in _154_miscstrings.cst.