The role of a seal is to prevent fluid leakage as well as preventing dust and debris from entering a component. It is always recommended to replace seals when worn, perished or when assembly replacements take place.
A gasket is a shaped sheet often made from rubber, paper or cork. Its role is to fill a space between two parts and act as a seal, thus preventing leakage into or from the parts when under compression. The Exhaust Manifold Gasket will specifically prevent