Also known as Cranesbill Geranium or Wild Geranium. The photo is a 'tame' version, but the looks are about the same. The wild ones here in the woods have lavender flowers and plain green leaves, but this would let you identify one if you ran across it.
It is a fairly good sized plant, making a mound of foliage about 18 inches tall. It grows in rich woods in the Eastern United States and Canada, about as far south as Georgia.
Medicinally, the leaves are gathered and dried to use in an infusion as a mild astringent. The infusions of the leaves are said to also be useful as a gargle for sore throat and for ulcerated mouth. The leaves are collected just before the plant flowers and when the tannin content is at hits highest.
As far as the garden variety goes, I had tried on many years ago without much success and so I avoided them as 'difficult'. That couldn't be farther from the truth. They are easy to grow, quickly forming a clump, and they flower freely starting in the spring with a full bloom, and then sproadically over the summer. Flower colors include the lavender of the wild version plus a variety of pastels including some with splashes of a second color on the petals. These are highly recommended and I will continue to add new ones to the gardens as I find places for them.