"Could is the past tense of CAN

Would is the past tense of WILL"---Julie

 Wonderful answer  Julie   

   Also,  we can  also expand the  consideration and show that the word "want"  also derives from  WILL.

 I can learn from you.  I could learn from you. I will learn from you.

I would learn from you. I want to learn from you.  I will learn from you.

   Can you be my teacher.  Would you be my teacher.  Will you be my teacher.

Could you be my teacher.  I will if I want to. I will if you will.  I can if you can.

I could if you could.. 

COULD, SHOULD and WOULD

Part 1 http://www.italki.com/entry/449564

.

.

Part 2 http://www.italki.com/entry/449565

.

.

Part 3 http://www.italki.com/entry/449566

.

.

Part 4 http://www.italki.com/entry/449567

Thank you Julie.

It depends on the context Samiya, however perhaps this is easy to remember:

Could is the past tense of CAN

Would is the past tense of WILL

Both can be used in many different circumstances as demonstrated in other responses.  However, it is often used in requests (nice polite ones!)

Could you please pass me the salt?

Could you help me with my English homework please?

Examples of would in the past tense might be:

He would never finish his homework on time.

She would never help her sister clean the house.

Of course, as this is the English language...there are many other uses of both words, depends on context!

Thank you bruce