With the exception of perennials that occupy a permanent position (rhubarb for example), vegetables are sown or planted afresh each year. It is a good idea to grow them in different places from one year to the next. This will prevent the soil from becoming exhausted by the same crop continually taking the same nutrients out of it. It also reduces the risk of pests and diseases.
This is an example of a five year crop rotation
Year 1: Brassicas
Year 2: Peas & Beans
Year 3: Potatoes and Fruiting Vegetables
Year 4: Onion Family
Year 5: Root vegetables
It is not so critical to rotate other vegetables such as squashes & salads.