In XenForo 2 the default style has 24 ad locations as predefined. Here is how each of them is placed in the layout of the default style.
XenForo’s default style provides 19 ad locations. Here is the visual guide to how each one of them is placed.
The complete visual guide to the position of each XenForo hook for header, footer as well as the forum_list, forum_view, thread_view and member_view pages