Traditional vs. Laser Engraving
With traditional engraving, the inscription is etched into the metal using a diamond tipped stylus.  The look is very elegant, and it's the best choice for polished stainless, sterling silver or gold jewelry. 
Example of traditional etched engraving Example of black lasered engraving
Traditional Etched Engraving Black Lasered Engraving

Laser engraving creates a solid black inscription by bonding a ceramic layer onto the stainless steel.  While not as elegant as traditional engraving, the black laser inscription is easier to read, and will remain legible.  It's the ideal choice for kids medical id's as well as medical bracelets for adults, but laser engraving is not available for sterling silver or gold.