The difference between: can/could, may/might, will/would, that/which

Can anybody explain me the exact difference between the usage of following (with examples please)...

Can/Could
May/Might
Will/Would
That/Which

"could","might","would" have a slighter tone and often show a degree of respect, I think.

"Can" is definite: He "can" go to school. Whereas "could" is only a possibility: He "could" go to school.

They are both model verbs indicating that something may/might happen. "May" is a possibility indicating that something could happen: May we go to school. But "may" can also be used to affirm something: You may go to school. "May" can be used in a few other ways too. Whereas "might," also similar, has different sub-uses: With considerable might he picked up the school house. It can also be used as a possibility: might we go to school; or, we might go to school. It can also be used to indicate that somebody should have done something: You might have told me he picked up the school.

Sorry I don't have time to answer the other two. I'll check back later to make sure somebody else answered them all.

Can = present tense, is able to
Could = past tense, was able to; future tense, will be able to or possibly will be able to

May and might tend to be used interchangeably with the meaning of "possibly be able to" in the future

We've covered that/which in another thread:
http://www.essayforum.com/essay-writing-feedback-3/advertise ments-affects-consumer-goods-ielts-preparing-7043/#msg32444

I'm going to send you to a grammar book for "would" as this is used as an auxiliary to verbs in several different instances.

Sounds like something you could probably just ask the overmind. Wikipedia has a pretty good discussion of auxiliary verbs here http://en.wikipedia.org/wiki/Auxiliary_verb, though you will have to search a bit more for a full explanation of all of the items on your list.