Firstly, just to be clear, this article is not about tools designed for the use of cats. That would be a different article. CAT stands for Computer Assisted Translation, and refers to the various productivity tools available to the 21st century translator. CAT is not the same as machine translation, where a translation is produced (often badly) by a computer.
Rather, CAT tools help to automate easily-automatable parts of the translation process, leaving the human (that’s you) to focus on the real business of translating. As an example, a CAT tool might help you to automatically translate all instances of «Le Comte de Monte Cristo» as “The Count of Monte Cristo”, saving you from doing the leg(finger)work. Or it might suggest a pre-defined translation of a technical term or brand name, stored in a Translation Memory (we’ll come to these later), saving you from searching for the correct translation each time you come across it.