Literal mode is often the safest first choice
Literal mode replaces every occurrence of the exact text inside the targeted cells. It is easy to reason about and avoids regex surprises. A blank find string is blocked because replacing an empty match can insert text between every character and produce a very different file.
Regex applies to the search, not capture expansion in the replacement
Regex mode treats the find field as a JavaScript regular expression. The replacement field is returned as literal text, so strings such as $1 are not expanded as capture references. That distinction matters if you are coming from editors that support backreference replacement.
Matching is case-sensitive
Literal and Regex modes are case-sensitive here, and there is no regex-flags input. Tokyo and TOKYO are separate cases. If your data has casing variants, normalize them first or run deliberate passes rather than assuming an ignore-case option.
Targeting one column reduces collateral changes
All-columns replacement is convenient, but the same text may also appear in IDs, notes, or URLs. If you know the change belongs only in a category, city, or status column, target that header. A replacement count much larger than expected is a useful warning sign.
A practical example
Replace an old host name only in a URL column, or standardize a category code across a catalog export. Keep the original CSV and review a few changed rows before you use the output in an import job.
If you want the deeper picture