Those are "broom". There are two genera with that common name, Cytissus & Genista, but I believe the differences between the genera are the sorts of things only a trained botanist would notice.

Broom is a flowering shrub in the pea family (Leguminosae, or Fabaceae, the family has two different Latin names, both used). It's lovely when it blooms, but most of the year what you will see are naked green stems. You'll notice they also have leaves now, but if I understand correctly the leaves will fall off during the summer and then you'll be left with all the thin, very flexible stems, and THEN you will understand why they are called "broom"!

You have Cytisus. The differences between the two genera are rather distinct - Genista has alternate leaves held singly, Cytisus has trifoliate leaves. Genista, to my knowledge, is only available with bright yellow flowers, while Cytisus scoparius and hybrids offer a wide range of colors. Genista, with the exception of some low, lax groundcover forms, is rather uncommon in this country as well.

Brooms tend to get a bad rap and in many cases, justifiably so as the species and some cultivars seed freely and the plant is listed as invasive in a number of western states. But many of the forms offering colors other than the standard yellow are sterile hybrids and pose no threat. There are few other shrubs that can offer such an intense explosion of color to the late spring garden, but that and their tolerance of poor, dry soils is about the limit of their appeal.