Translation: a matter of source?

Question: you need a translation for your document and your translator starts to speak about source text and words, target text and words. And it’s all greek to you! (By the way, in French, we say it’s Chinese!). Why is there a source (water?) and a target (archery?)?
Actually your translator wants to explain that your document is the original text, and the translation of your document will constitute the translated text.
It is useful also because very often, to make an exact quote for a translation, the translator needs to know how many words there are in it. Reason: the price of a translation is often (but not always) a price per word and the number of words in the original (or source) text is already known (There is a function on your computer giving this number) whereas the number of words in the final (or target) text is different… And you do not know it from the beginning because you do not know the words the translator will use to do the job. For example: 100 English words require, approximately, 120 words in French. And 100 German words require approximately 130 words in French! And these are only approximate figures, it may be more… or less. So it’s easier for you to know the exact price before the translator starts to work for you.
Do you want to know more about my translation services to help you? Feel free to contact me, I will be pleased to answer your requests.