It looks like you have two different plants there -
I'm wondering if the brighter green one is chickweed (Stella media)?
It is a common annual - quite nice as a salad leaf. I can't really tell from the photo though.
The other looks like some sort of Oxalis - maybe oxalis corniculata:
That can be invasive I gather depending on your climate. Again edible leaves, although tend to be a bit tough in my experience.