Exhaust wrap are used to wrap exhaust manifolds, downpipes and exhause systems on different types of vehicles. There are two main reasons to wrap your exhaust parts. One of them is to reduce radiant heat from the exhaust parts to prevent damage of parts nearby. This also lowers the engine bay temperature.
One other advantage is to wrap the exhaust manifold which makes the exhaust gases hotter and thereby keep the gas speed which is positive for engine performance.