Andii, she is using container gardening, very similar to raised bed gardening. the red trays are made for tomatoes. the red helps the tomatoes turn the energy from the sun into an easier-to-use format for the tomatoes. I know that's a shoddy explanation, but it works. I tend to use red plastic around my tomatoes. the trays also tend to reduce bugs. the benefit of this kind of gardening is that you don't need to dig into rocky soil, the soil is better because you make it, and harvest of rooted veggies is much simpler. Check out the gardengirltv.com or squarefootgardening.com for more info.
Laurie