Could = Is it possible to.... (Can ANYONE do it?)

Would = Are you willing to.... (Can YOU do it?)

Although both are directed at one person, Could is a more indirect way of asking.

Check your grammar book for modal verbs.

https://learnenglish.britishcouncil.org/en/english-grammar/modal-verbs

"Could" means the <font style="background-color: yellow;">capability</font> to do something in the past or future. Ex: When I was younger, I could stay awake all night and still have energy for the next morning. (for past) OR I could help you study for your exams next week. (for future)

"Would" on the other hand means the <font style="background-color: yellow;">willingness</font> to do something in the future. Ex. If you do what I asked, I would pay you enough money.

In addition, there is also "Should" which shows the need for someone to do something. Ex. You should take your medicine as prescribed.

For easy reference (present tense):

Could - Can

Would - Will

Should - Shall

Note: Verbs following these three words should be in the infinitive form.

You can also use these words when asking questions / favors to be polite.

Ex. Could you... / I would like to...

I hope these could help.