Embossing is a forming operation used to create indentation in the sheet, such as raised (indented) lettering or strengthening rips, as shown in fig. Some stretching and thinning of the metal are involved. The operation may seem similar to coining.
Coining is a bulk deformation operation. It is frequently used in sheet-metal work to form indentation and raised section in the part. Indentation result in thinning of the sheet-metal and the raised section result in thickening of the metal.