A CAT tool is a Computer-Assisted (or -Aided) Translation program. The software helps translators work more efficiently by remembering previous translation choices. It is not Machine Translation (MT), which instead attempts to provide a translation for the text as a whole by converting (often unsuccessfully) the words from one language into another. A CAT tool will only offer a translation suggestion if there is a phrase or sentence that is exactly the same or highly similar in its translation memory (TM).
Please see the Software Comparison Tool on Proz.com for a more complete list of CATs with details of their features, ratings and reviews.
You might find it useful to read the following posts on CATs: Percy Balemans’ article ‘The usefulness of CAT tools’; Claire Cox’s comparison of ‘Wordfast Classic and Trados Studio 2014′; Emma Goldsmith’s comparisons of SDL Trados Studio and Déjà Vu, and SDL Trados Studio and memoQ. Emma regularly writes about CAT tools, so please check her blog for more articles of interest. Francesco Pugliano has also compared CAT tools in easy-to-understand tables. Lastly, Simon Akhrameev has reviewed the free online MateCat tool.
Rafa Lombardino has also produced some short videos that explain how CAT tools work.
For more posts of interest on CATs, please see the relevant section on the Articles of Special Interest to New Translators page on this blog.
After being a user of Wordfast Classic for many years, I switched to using memoQ in the summer of 2017 because of ongoing problems with Wordfast in the latest Windows and Word software. Below you’ll find a list of posts on my memoQ journey as I learn how to use a CAT that is far more complex than the simpler Wordfast.