This is the white dapperling mushroom, sometimes it looks very much like the death cap. It shows up in grassy areas just like the death cap mushroom, it fruits in large groups. The mushroom is considered edible with caution, both because it can be confused with the Deathcap and the Destroying Angel. Some people who have eaten the White Dapperling have become ill, a few have even been hospitalized, so my advice is to just leave this one alone.
The cap starts out rounded, then gradually flattens out to become convex with a depressed center. The surface seems dull, not shiny, and its color is commonly white to an off-white cream color. The flesh of the cap is white and thick. This is a variable species that can be quite small to quite large. Old specimens can have a grayish color to the cap and some will turn light brown. When scratched, you will see a yellow to pinkish color on some.
I find these mushrooms to be very pretty when growing on a green lawn, sometimes they will even form a fairy circle.