Technically, would is the past tense of will, but it is an auxiliary verb that has many uses, some of which even express the present tense.

Would is future tense?

We use would as the past of will, to describe past beliefs about the future: I thought we would be late, so we would have to take the train.

How would is used in past tense?

We can use would to talk about repeated past actions that don't happen any more. Every Saturday I would go on a long bike ride. My dad would read me amazing stories every night at bedtime. would for past habits is slightly more formal than used to.