The four types of OCD are:
Contamination-related. These people are obsessed with thoughts of germs, disease, and filth. They may be afraid to touch anything that may be risky to them, including things like door handles, faucets, toilets, etc. They may engage in compulsive behaviors like repeated hand washing, showering, or disinfecting.
Perfection-related. These people are obsessed with thoughts of order, organization, or symmetry. They may be afraid that something will get lost, or something bad will happen if things aren't perfect. They may spend lots of time arranging and rearranging things, putting things in certain orders, counting objects, superstition, or hoarding objects.
Doubt-related. These people constantly fear that they forgot something and something bad will happen as a result. They may check and recheck that they turned the oven off, that they switched the light off, or that they locked the door.
Taboo thinking. These people find themselves thinking violent, sexual, or religious thoughts that violate their personal values. They may go through rituals of prayer or thought to "cancel out" taboo thoughts.