Squashes are native to the Americas. Pumpkins and zucchini are just two among hundreds of types of squashes.
Summer and winter squash are both planted in spring. The difference is that winter squash is allowed to ripen fully, hardening the skin to provide for winter storage, while summer squash is harvested young and tender.
For seed saving, squash need to ripen, change color and harden to produce viable seeds. Varieties of the same species need 1/2 mile of isolation for true seeds.