The idea of crop rotation is to grow groups of vegetables on a different part of the plot each year by rotating them over a 3 or 4 year period. This helps to reduce the build up of pest and disease problems which are crop specific and allows you to group crops together according to their individual growing requirements. Soil can also be depleted of nutrients, also called 'Soil sickness', causing crop yields to deteriorate which can be avoided by crop rotation.
What are the Plant Groups?
How to practice crop rotation?
Divide your vegetable garden or allotment into four areas to use for crop rotation. Rotate each section of your plot by one each year (in the order shown below) so that Brassicas follow Legumes, Legumes follow Alliums/Roots, Alliums follow Potatoes and Potatoes follow Brassicas
The above gives a basic overview of Crop Rotation for more information on How it all works see Crop Rotation in the Growing Advice section.