It's particularly effective at protecting against leaks of water, oils, hydrocarbons and silicone greases, and offers better performance under high temperatures than neoprene alternatives.
A gasket sheet - often referred to as 'gasket paper', despite usually being made from silicone rubber, cork, nitrile or any other robust flexible material - is a large piece of sheeting intended to be used in making quick, cost-effective gaskets (seals), for joining surfaces or components together.