There are three different types of fairy rings, classified by how they look. You can t actually see the first type of fairy ring until the fruiting bodies pop up, and make a temporary circle of mushrooms. In the second type of fairy ring, there is a rather vigorous growth of the grass. The third type of fairy ring shows the opposite - bare or damaged patches of grass. Here, the underground mass of fungus is so dense that it stops the water and nutrients from getting to the roots of the grass.
Plants have seeds, but in the fungus world, the equivalent of a seed is a spore.
When a spore lands on suitable ground, which is normally richly fertilised, it will grow and turn into this cottonwool-like mass of mycelium. These fungal threads are the actual body of the fungus. As it grows outwards, the outer edge is always alive, while the inner central part eventually dies. The fungus eats differently from us. We humans eat with our mouths, and then we digest or break down the food with chemicals inside our gut.