No, they happen extremely often. If X is a word that starts with a vowel, or a silent 'h' you will get a contraction for the following:
Je + X = J'X (e.g. j'ai)
le + X = l'X (e.g. l'homme)
la + X = l'X (e.g. l'eau)
de + X = d'X (e.g. d'une)
que + X = qu'X (e.g. qu'on)
There are also some not so obvious contractions, (or words you didn't realize are contractions):
à + le = au
de + le = du
de + les = des
There are a lot more, and they are intimidating at first, but the patterns will be obvious as you go. The point of a contraction is to make the words flow together.
Yes to an extent, this is because the word "de" is a partitive article, which is an article that expresses an unknown quantity of something in general. To be exact, it acts as an indefinite plural article which doesn't exist in English. "J'ai du lait." --> "I have (some) milk." You might run into a situation where you want to say you like something in general. You would have to say "les" instead of "des". This is because appreciation verbs don't go along with partitive articles in context. "J'aime des frites. I like fries" is incorrect. "J'aime les frites. I like fries" is correct. Even though the word "the" is not present when translated, this helps avoid grammatical errors when expressing things you like in general.
The articles work like this:
- Un chat, des chats = a cat, cats
- Une pomme, des pommes = an apple, apples
- un homme, des hommes = a man, men
- une femme, des femmes = a woman, women
I.e., "des" in this situation represents the plural of "un" or "une". There is no counterpart for this in English (although some people use "some", it is not entirely correct).
"Des" is the plural of "un/une". I.e., "un chat" = a cat and "des chats" = cats. What word do we use to translate "des". Well, nothing really, because English does not have an actual counterpart for the plural article. Here are some other examples:
- un homme (a man), l'homme = the man, les hommes = the men, des hommes = men.
- une pomme (an apple), la pomme = the apple, les pommes = the apples, des pommes = apples.