button-activate is a compiled Lisp function in `button.el'.

(button-activate BUTTON &optional USE-MOUSE-ACTION)

Call BUTTON's action property.
If USE-MOUSE-ACTION is non-nil, invoke the button's mouse-action
instead of its normal action; if the button has no mouse-action,
the normal action is used instead.

The action can either be a marker or a function. If it's a
marker then goto it. Otherwise it it is a function then it is
called with BUTTON as only argument. BUTTON is either an
overlay, a buffer position, or (for buttons in the mode-line or
header-line) a string.