Machine Translation means a text being translated by a computer program which uses a range of algorithms and linguistic and statistical rules as well as various dictionaries applied to the text to be translated. Currently, work is being done to optimize MT - a tendency which the industry is following with great interest and increasing success.
The objective of this state of the art technology is on the one hand, to translate texts which are not perfect, or linguistically correct, but "only" need to be understood (internal correspondence, chats, etc.) and on the other hand, to provide a cheap "raw translation" which can retrospectively be checked and corrected by a human translator.
Computer-aided translation is always carried out by human translators. However, with CAT systems, all translated text segments are saved in the source and target language in a database (Translation Memory - TM). This means they are available for future translations and the translator can either apply them directly or check and adapt them.
The tools used for computer-aided translation are called Translation Memory Systems (TMS). Apart from the aforementioned database, and Translation Memory, they consist of the an editor that the translator works in as well as a terminology component, thus offering comprehensive quality assurance functions.