Breadboard ends are narrow boards (4"-7" wide) that are mechanically joined to the ends of a larger panel. The purpose is to support and maintain the rigidity of the panel, while allowing the panel to shrink or expand across the grain.
 
With higher quality materials, breadboard ends are now more aesthetic than functinal but they still have to be properly installed to keep your table from buckling or cracking.
 
At TruCraft we spend around 4 hours properly installing a pair of breadboards.