Square foot gardening is a method of gardening which was created by Mel Bartholomew, an american retired engineer. He made the observation that in a traditional garden, we spend time taking care of the not used parts such as the paths between rows. We as well often water those and simply lose the related water. Last but not least of his observation, in a traditional garden, we usually sow a full row of a given crop, result is that we have too much of that one and would have loved another one but have no space for it anymore.
From that, Mel designed a 4 x 4 foot growing area which he then sub-divide in 16 area of 1 square foot each. Each of those can then allocate a different crop.