Quel means “which”, but in some cases, you can also translate it as “what”.

For example:

Quel est ton animal préféré ?

means: “What is your favorite animal?”.

On this question you have to answer which animal you like most.
(Yeah, I know, it can also be “what your favorite animal is”, but you can say “which” here!)

Que is most used for asking questions like: “What do you eat?”

Example:

Que manges-tu ?

is translated as: “What are you eating?”

What you have to answer is what you are eating.

Note:
Que can only be used in the following forms of questions:

• “est-ce que” (Qu’est-ce que vous dites?)
• inversion (Que dites-vous?)

and not in questions with intonation! Then que will be replaced with quoi:

Tu manges quoi ?