{debug} dumps the debug console to the page. This works regardless of the debug settings in the php script. Since this gets executed at runtime, this is only able to show the assigned variables; not the templates that are in use. However, you can see all the currently available variables within the scope of a template.

If caching is enabled and a page is loaded from cache {debug} does show only the variables which assigned for the cached page.

In order to see also the variables which have been locally assigned within the template it does make sense to place the {debug} tag at the end of the template.

See also the debugging console page.