Similar to the jrCore_is_mobile_device() template block, the jrCore_is_tablet_device() function tries to detect if the person viewing the page is viewing it via a tablet device.
If the function thinks the device IS a tablet, it will return TRUE.
So using this {if} template block will only sow the contents to users who are looking at the page on a tablet device.
Example
The example below tries to dectect if the devices is a tablet device, and if it finds that it is, then include the 'header_menu_mobile.tpl' file from the current skin.