Que can change
When followed by a vowel (a, e, i, o, u, y), que becomes qu’
- J’irai à la boulangerie qu’il choisira.
One spelling, several words
Que actually has several uses. It’s not always a pronom relatif. e.g.
- Je pense que tu as raison.
- Il n’a que 10 euros.
- Tu as l’air plus content qu’avant.
- If this makes things confusing, just think of que as simply many words that happen to share the same spelling.