What exactly is toilette is it woman's dress or WC or perfume or makeup table and why all these are called toilette can anybody tell what the relationship between these toilette-related things is?

Answer 1

"La toilette" (fem.) is an old fashioned word for washing up yourself and get pretty. It is still used in that sense in "faire sa toilette". Ladies used to do that in front of ornate tables, which were called in the same way by extension (a sense of the word that you will find only in 19th-century literature).

In that process of getting neat, clean, many uses some "eau de toilette", a kind of perfume. It was named this because you used it while doing your "toilette". The word is still in use to speak of a kind of perfume that is less strong and concentrated.

As getting neat and attractive was often before going out, you had to get well dressed, hence the word spread to clothing. That sense of the word is now nearly out of use, but suggested pretty dresses and other delicate feminine clothing, with the purpose of being well-dressed, so we're not speaking of underwear here.

Finally, "les toilettes" (feminine and plural) are the WC. It is less prestigious but still related to cleaning, in the same manner that the English-speaking world often use "bathroom" for the loo, even though you don't take any baths in there. "Où sont les toilettes ?" (where is the bathroom/loo) is still a very useful sentence to know in modern French.