Your car’s head gasket probably never comes to mind until something goes wrong. Since this is the piece that is between your cylinder heads and the cylinder block, it’s a fairly vital part that doesn’t need too much attention until there is a crack, which can cause some leaking.
The head gasket is there to maintain compression while also preventing leakage of coolant and oil into the cylinders. If there’s a leak or issue, it should be dealt with soon so that no further problems occur. A blown head gasket is far more expensive to deal with, so a band-aid solution is to use a head gasket sealer.