The Meadow Mushroom, or Agaricus campestris, is a common edible mushroom that is good eaten raw or cooked. As a member of the Agaricus family, it is closely related to the common white mushrooms you buy in the grocery store and it can be used in the kitchen in the same capacities. However, you will find that this wild variety has a lot more flavor.
Examine the mushroom's cap. The Meadow Mushroom's cap is white and smooth and slightly rounded until the mushroom gets old and starts to dry up. After that they flatten out a bit, but at that point they are not very good for eating.
Look under the cap to see what the gills look like. The gills are light pink when the mushroom is young and change to a dark brown with maturity. Because of these pink gills, the Meadow Mushroom is sometimes called the "Pink Bottom."
Study the stalk. Like the cap, the stalk is white and smooth. It may also be somewhat fibrous toward the bottom.
Observe that this is a veiled mushroom. The veil is a thin ring around the stalk, where the edges of the cap were attached before the mushroom sprung up.
Look at the growth location. As both the variety name "campestris" and the common name implies, the Meadow Mushroom grows in grasslands. Nowadays that often means it is found in the lawn. Agaricus campestris may appear scattered here and there in the grass, but there are generally more than one in an area. Often they grow in fairy rings, which is one of the more delightful things about them. You can spot a fairy ring even before the mushrooms appear. It will look like a ring in the grass where the grass is darker green and more lush.