I believe "regular soil," as used in one of the questions above, just refers to soil that isn't specifically for potting, i.e. the potting soil you buy in stores. Regular soil would be what you find in your backyard. Potting soil, as sold in stores, is very rich in nutrients and is better for potted plants.

"Regular" is probably the key word. In nature regular soil is packed with all kinds of microbes. This is one of the most important elements there are to growing healthy plants and vegetables. Dirt contains all kinds of minerals and nutrients, but if they can not be accessed or absorbed properly by plants then their benefits are useless. So, regular soil is composed of earth minerals combined with decayed or decaying organic material (such as leaves, dead plants or critters, etc) and billions of microbes. As an example, it is certain fungi on roots which help a plant to absorb nutrients. There are literally thousands and thousands of different kinds of microbes in regular soil. That is the real key which is often overlooked. Chemical fertilizers and pesticides upset this natural way where the microbes of regular soil assist plants. As a result, non-organic vegetables have far less nutrients than organic vegetables. These microbes actually even balance pests in themselves (example: some fungi will attack ants or grubs) or just provide healthy plants. Pests tend to lean towards distressed plants. So, regular soil is alive and processes the nutrients needed for assimilation by the plant. It is the key element to that transformation from dirt to plant. Just like you wouldn't go out and eat a cup of dirt for dinner -- it needs to be processed or transformed by plants and/or animals first. Plants are our link to getting nutrients. Microbes in the soil are the link for plants to get nutrients. By avoiding chemical fertilizers and pesticides, one improves the health of the soil. Even Miracle Grow (owned by Scotts, the number one provider of lawn "care" products, who excels with propaganda lies) is just a chemical and makes your soil less a "regular soil". There are many natural ways to improve soil and its available nutrients. Some great information is available at www.dirtdoctor.com