That's a red oak (pointed tips of the leaves give it away) as to particular species, where are you located? There are many, many oak tree species but they are easier to narrow down if you know the location they grow in.
It's some variety of red oak, the pointy leaf tips are a hallmark of red oaks. Where about on the globe are you located, and is that as large as a mature acorn from the tree gets? It seems small, and will help narrow down the type of tree.
"Study books and observe nature; if they do not agree, throw away the books." ~ William A. Albrecht