As Ben wrote, it is Lamium purpureum. It is also the typus (the official representative) of Lamium (genus), and of the large family of Lamiaceae (family, previously also know as Labiatae).
Later you will probably seen his brower Lamium maculatum, which has larger flowers and with some more distance between flowers.
Most of Lamiaceae have such typical flower, usually with a label, 4 anthers (often 2 long and two short). Typical is also the square stem and perfume to odor.
Basilicum, rosemary, thyme, lavender, etc are gardening plant of such family.
The white flowers in the same photos are Stellaria media, you have Taraxacum, I think Arabis turita (or something similar), I think also a Vicia and a Trifolium. You have a lot of diversity on weeds ;-)