I think it’s a type of shrub, but I was told it’s a white poinsettia plant. It’s very wiry and has green leaves all year round except for winter and spring. The white flowers come in during the winter and the leaves begin to fall off. When spring comes the white flowers turn pink. Some people keep them as bushes, but I’ve seen people grow them as trees that are 15-20 feet high.
I think Giacomo Catenazzi is right that some people may call this plant a "white poinsettia" because of its structural similarity to a poinsettia (the showy bracts surrounding the small true flowers in the center).
Additionally, from your photo, the leaves look like they might have a texture something like poinsettia leaves.
I was able to find a photo at "Proven Winners" Plant Nursery of what they call "Diamond Delight® Euphorbia hybrid". It looks a lot like your plant, and is in the same genus as poinsettias (namely "Euphorbia").
TopTropicals.com also has a picture of another Euphorbia that looks very much like your plant. This one is called Euphorbia leucocephala, and it even has those reddish stems:
I think your plant is a Euphorbia and pretty closely related to these two. I can see why someone might call your shrub a "white poinsettia", but it is a confusing name for it since regular poinsettias do also come in white. What people usually mean by "white poinsettias" look just like the Christmassy poinsettias we are used to with the large pointy jagged bracts, but white instead of red.