Many have used translation software or translation tool to help them translate texts, but actually the term "translation software" is vague because any software related to translation can be called a translation software, no matter how different they are. So, what do you really mean by saying "translation software"?
There are two kinds of translation software: machine translation (MT, or automated translation, instant translation) and computer-assisted translation (CAT). Both are two separate concepts.
People have long dreamed of fast, accurate, and affordable translations. With the advancement of computer technology in the modern age, we hope that this dream would be 100% fulfilled by MT. However, even to this day, the quality of machine translation leaves much to be desired. The translation of many texts (such as this one) still relies heavily on the work of an expert human translator, and this is where CAT comes into play.
In the 1970s, computer engineers began developing CAT tools to help improve the speed and accuracy of human translators. In other words, CAT is for translators. So if you are not a professional translator, you would find CAT is totally useless for you because it does not automatically generate the translation you want.
With this in mind, now we can tell the differences between MT and CAT:
Machine translation (MT)
Source texts are completed translated by machines (computer algorithms), with no humans involved throughout the process. Since humans are not part of the translation process, the accuracy of the translated text is often subpar and require human post-editing.
The advantages of MT include cost and speed. Computers can process a large amount of text almost instantly. If you are an end user of machines translation, you can go to any of the MT website, i.g., Google Translate to get your translation for free. But always remember that the accuracy of the MT is still limited today and it is not a good idea to use the translation you get from it in formal occasions, such as pitching or lecturing.
Computer-assisted translation (CAT)
Source texts are translated by humans, who are aided by functions that can improve the speed and accuracy of the translation in the process. The most well-known function for improving the efficiency of the translation process is the translation memory (TM, databases of texts in multiple languages) and terminology databases (to help translators save and reuse terminology efficiently).
Many CATs have MT built in for translators. Usually, translators do not rely on MT but sometimes they do use it as a reference. In what circumstances would translators adopt a translation offered by MT? In most cases, they use MT when the meaning and the structure of the source text is relatively simple. In this case, they would apply the translation generated by the machine and make some changes to it.
MT: If you are talking about instant translation without human touch and does not cost you a dime, you are talking about machine translation.
CAT: If you are talking about the software that help boosts the human translator's efficiency, you are talking about computer-assisted translation. CAT is not for ordinary users!