Generic functions signature

PDF, Chapter 8: Generics, Paragraph Creating Generic FunctionsImplementing the Function:

Node<E>? createTree<E>(…) { … }

Can’t figure out where does the <E> in the function name createTree<E> come from? I didn’t see that signature in the previous chapters and the previous book — we always use just the functionName() syntaxis without angle brackets after the function name.

Can you explain it a little bit?