These compounds all contain calcium in different oxidation states.

Ca - calcium in its elemental form
CaO - calcium oxide (calcium in oxidation state +2)
Ca(OH)2 - calcium hydroxide (calcium in oxidation state +2)
CaCO3 - calcium carbonate (calcium in oxidation state +2)
CaCo2 - this is not a standard chemical formula. It appears to be a typo, as CaCo2 should actually be written as CaCO2 - calcium carbonate in the molecular form with two oxygen atoms.