Callers - Use the arrow to the right of this contextual menu option for a complete list of all of the functions that called the selected function. Choosing a function from this list selects it in the hierarchy. If the function is the root function, this option is grayed out.

Callees - This menu option works identically to the 'Callers' menu option, only it contains a selectable list of functions that are called by the selected function. If the selected function does not call any functions, this menu option is grayed out.