Gaskets are found in the space between many components in a vehicle which need that gap sealed. Many materials, especially dissimilar metals, don't seal well on their own, and gaskets are used to fix this problem. They are often made out of moderately soft materials which can withstand a large amount of heat and pressure.
Sometimes when a component needs a gasket but one isn't available, or there is a custom part which no one would make a gasket for, gasket makers are used. There are a wide variety of gasket makers available, including oil resistant, high temperature, coolant resistant, copper-infused, rigid/high torque, and some that don't solidify.
Choosing the right gasket maker for the particular part connection. In some situations, a formed gasket can work better than a pre-molded gasket, while in other situations, such as when replacing head gaskets, no gasket maker can handle the stresses.