What is the difference between graphite oxide and graphene oxide?
In short, graphite is several graphene sheets piled one above another.

Graphene is made up of one single sheet of carbon atoms arranged in hexagonal pattern (like a honeycomb), and graphite are several such sheets, each sheet linked to another by weak intermolecular forces, which gives the graphite its lubricative properties.

EDIT:
Similarly, graphene oxide is a layer of graphene with oxygen atoms, $OH$ groups and $COOH$ groups attached to it, while graphite oxide are layers of graphene oxide.

Because of the presence of $COOH$ groups, graphite oxide can disperse in basic solutions (or even water!) to give graphene oxide.

$CO_2$ is simply carbon dioxide, one carbon atom doubly bonded two two oxygen atoms.

By contrast, graphite oxide is like a huge field of carbon with the groups I mentioned earlier while carbon dioxide is like a small ball.