Often mistaken for clover. The common ones with yellow flowers is considered a weed and will take over your yard. Their flowers smell good, and you can eat them (also called sour grass), but too much would keep you from absorbing calcium!
True clover flowers are pink or white pom-poms. Single stems and low to the ground. They often have stripes.
These are an edible weed. They branch, fan out, and grow burr seeds that can be painful if stuck in pet paws.