tomato growing inside a tomato ,strange or what?

Garden centre

• 
  Tomato F1 Beefeater Seeds
  £4.25 at Suttons Seeds
• 
  Tomato 'Costoluto Fiorentino' (Beefsteak Tomato)
  £1.89 at Crocus
• 
  Tomato 'Principe Borghese' (Tomato)
  £1.89 at Crocus
• 
  Tomato Gourmet Seeds (Gro Sure)
  £3.99 at Unwins
• 
  Tomato Ailsa Craig Seeds
  £1.49 at Unwins