Square foot gardening is the (often edible gardening) technique where a garden's area is divided into squares, often 1' by 1', hence the name, and plants are assigned to a square plot. In comparison with more traditional row gardening, plants are packed together as closely as possible. I started gardening this way last year and love it for it's efficiency, yields, and simplicity.
If you're limited on space, square foot gardening a great way to pack your annual edibles into smaller areas. While there is some criticism that this "crowding" of plants will limit root production and thus plant production based on competition for water and nutrients, I didn't find this to be the case. You do, however, have to be very diligent about adding compost and organic plant food throughout the season; I would recommend using a cover crop such as fava beans to add nitrogen and loam to your soil. Planting so many plants close together will be more intensive on the soil, but plan for this by prepping and feeding your beds accordingly.