"The girl buys the dress that she wants."
Translation:La fille achète la robe qu'elle veut.
Am i understanding the que vs. Qui issue here: "Il sait que le livre qui est sur la table appartient à Paul"
The first que simple 'introduces' further information about some1/thing and the 2nd qui is used because "the book" is the object of the second part of the sentance?
So "the girl buys the dress THAT she wants" is que because it simply introduces extra info again here?
You understood correctly, but the rule is simpler:
he knows (that) the book is there = il sait que le livre est là: "que" is a conjunction, linking main clause "he knows/il sait" and subordinate clause "the book is there/le livre est là" - in English, you can drop it; in French, you can't.
he knows the book that is on the table = il connaît le livre qui est sur la table: "qui" is a relative pronoun, it represents "book/livre" (= its antecedent) in the relative clause and it is subject of "is/est".
he knows the book that I like = il connaît le livre que j'aime: "que" is a relative pronoun, it represents "book/livre" (= its antecedent) in the relative clause and it is direct object of "like" (subject is "I/je").
A few details here
The natural pronunciation of "que" is KUH. When "que" is placed before a word starting with a vowel sound, there would a vowel sound conflict with the sound UH. As a consequence, "que" is elided (drop the -e and replace it with an apostrophe, just to keep the K sound):
- qu'il, qu'elle, qu'on
The same applies to other little words: je, le, ne, me, te, se, de.
In this sentence "that" is not a demonstrative pronoun meaning "the thing there" (= cela/ça).
"that" is a relative pronoun, representing "dress" and the direct object of the verb "wants".
In French, the object relative pronoun is "que", with the same nature and function as in the English sentence.