Vegetable seeds come from vegetables. Vegetables come from vegetable seeds. You can buy vegetable seeds in the store and plant them, to grow plants that will grow vegetables, if they grow big enough and healthy enough.

This has been going on for about 400 million of years. Before the first seeds, plants came from spores, like ferns still do today. I recommend you to read the full story on seeds here.

Vegetables are plants. They grow in the soil like any other plant, their seeds come from the vegetables.