tree is sick
So far as we can tell from the photo, the tree is an elm. However, we can't be sure what species. Chances are it's an American elm and if so, it may be exhibiting symptoms of Dutch elm disease. If the disease is present, the photo indicates that the tree is beyond recovery.
For a certain identification and diagnosis, consider asking a forester or certified arborist to assess the tree's health onsite and recommend a course of action.
The following information may be useful if you decide to hire an arborist.
How to hire a professional arborist to help care for your landscape trees
Go here to learn more about Dutch elm disease: