An anvil is a hard piece of metal which is used as a workbench when making things out of iron or steel. An anvil is used by a blacksmith when they need to hammer hot iron to bend it into the shape they want. A blacksmith can make new shoes for horses.
Anvils were known in the Bronze Age and possibly earlier. They were used in Ancient Greece and Ancient Egypt. They are still in use today, although not nearly as much as 100 years ago when there were many more horses.
Anvils are extremely heavy. They are made in different sizes. The 17th century writer John Bunyan was a tinker (someone who mends pots and pans). He walked around the villages of Bedfordshire with a small anvil and a few tools on his back. His anvil was wedge-shaped, so that he could knock it into the ground when he needed to do a repair. His anvil is now in the John Bunyan museum in Bedford.