A red blend is a designation or description indicating that the bottle contains more than one grape variety. Red blends can be made in traditional style, such as a Bordeaux or Rhône wine, or with any combination of grapes that the winemaker desires, if it is in alignment with the local wine laws. Wine laws can dictate what grapes can be used and in what proportion.
Many wines that you are familiar with are blends including wines from Bordeaux and the Rhone valley. Wines labelled as Meritage, Cava and Port are blends. Champagne, Rioja and Priorat can be blends, too.