Thank you for sending the picture to us at eXtension.
That appears to be a hydrangea. There are many types of hydrangeas...too many for ME to keep track of! If you want to know exactly what type of hydrangea it is, I would either consider taking this picture to a local garden center or nursery, or going online to identify it.
If you go online, I would suggest going to the Missouri Botanical Garden Plant Finder website: http://www.missouribotanicalgarden.org/plantfinder/plantfindersearch.aspx . Type "hydrangea" into the search bar. A whole bunch of plant should come up. You can scan through them and look for those that look similar to your plant. Be sure to check for shape of the blossom cluster, as well as the leaves. And be sure that whichever hydrangea you look up is blooming at the same time as the one in your photo.