In a shot shell what protects the shot and or barrel and seals the gas behind the shot charge?

In a shotgun shell, the component that protects the shot and seals the gas behind the shot charge is called the wad. The wad serves to separate the shot from the powder charge, preventing the shot from being deformed and ensuring efficient gas sealing during firing. It also helps to stabilize the shot as it travels down the barrel, improving accuracy and reducing recoil.