difference between would and will

There are ample usages of would, not only it's used in past moments but when you offer something to someone then you could use it for politeness, like for example, would you like to have some candies? yes I would like and cold drink too. another usage of would is when you want to get someone's permission that would he/she do that for you because you are not pretty sure about that, like for instance would you get me some vegetables from vegetable store or rather green store? yes I will ( not I would) because he/ she wants to help you for sure

both are the helping verbs used in future tense... but will is used in future simple and would is used in future past.