Why protect specific keywords
A plain synonym-based rewrite can accidentally swap out the exact keyword phrase you are trying to rank for - replacing "running shoes" with "jogging footwear" defeats the purpose if search volume is concentrated on the original phrase. This runs the same paragraph-preserving rewrite engine as the Article Rewriter tool, but first builds a protected word list from the keywords you enter, so every word in those phrases is left untouched anywhere it appears in the text, while everything else gets rewritten normally.
Why protection works at the word level, not the exact phrase
Protecting at the individual-word level rather than the exact phrase means entering "running shoes" also keeps "running" safe in an unrelated sentence elsewhere in the article, and keeps "shoes" safe too - broader coverage than exact-phrase matching would give, which is useful since your target keyword often appears in slightly different word orders or combinations throughout a real article.
Why this matters more for SEO content specifically than general rewriting
General-purpose paraphrasing is fine when the goal is just varying wording, but SEO content usually has a specific phrase it needs to rank for - losing that exact phrase to a synonym swap, even a good one, can measurably hurt how well the page targets its intended search query. This tool exists specifically to solve that narrower problem the plain Article Rewriter doesn't address.
Why listing core words is enough, not every keyword variation
Because protection operates on individual words, listing just the core phrase ("running shoes") already protects every variation that reuses those same words ("best running shoes," "running shoes review," and so on) - there's no need to separately list every long-tail variation of your target phrase.