Identifying a Weed & Killing it
This looks like wild violets. They tend to grow in shady, moist areas but will infiltrate a lawn. In general, they are native, and they do have wildlife value. In particular, they are the larval food source for fritillary butterflies. You just may want to let some of them be depending upon where they are located.
It's a tough perennial weed to eliminate and they do spread prolifically.
In lawns early fall is the best time to get serious about some of the tougher lawn weeds. You will have to be persistent. Keep in mind that a perfect lawn is difficult to achieve in MD without a great deal of chemical application which doesn't happen without cost and environmental impact. Regular fall fertilization and mowing high are the two simple strategies that benefit lawns. Here is more about lawn care. Begin with a soil test. Result will give pH, and nutrient deficiencies
In ornamental beds- remove by using a weeding tool when the soil is moist.
The following link has more information about control