A fuzzy match is a translation memory suggestion whose source is similar to the new sentence but not identical, scored as a percentage (from 50% to 99% in most tools) that tells the translator how much editing it is likely to need.
The CAT tool compares the new source segment with the stored ones and measures how much text would have to change to turn one into the other. The fewer the changes, the higher the score. An identical sentence is a 100% match, not a fuzzy match. Each tool scores in its own way (some weigh numbers, tags or formatting differently), so the same pair of sentences can score a few points apart in Trados, memoQ and other tools.
TraduQ's word count and quote tool scores by characters: 1 minus the edit distance divided by the length of the longer sentence. A sentence that differs only in capitals or punctuation scores 99%, and anything below 50% counts as no match.
Analyses group fuzzy matches into bands. The quote tool uses seven bands, the same core bands as Trados and memoQ: repetitions, 100% matches, 95–99%, 85–94%, 75–84%, 50–74% and no match. The four middle bands are the fuzzy ones.
Translators usually charge a share of the full rate per band. The quote tool's defaults are one typical example, not a standard: 15% of the rate for 95–99%, 25% for 85–94%, 60% for 75–84% and the full rate for 50–74%. Agree the grid with your client before the job; the translation rates guide explains why.
The TM holds "The warranty covers parts and labour for two years." In the new text:
A low fuzzy match can take as long as translating from scratch, which is why the 50–74% band is often billed at the full rate.