The oxidation number of carbon changes from -1 to +4.
the oxidation number of oxygen changes from 0 to -2.
carbon is oxidized.
oxygen is reduced.
electrons are transferred from carbon to oxygen.

Carbon is oxidized because to increase of its oxidation number.
Oxygen is reduced because to decrease of its oxidation number.
If the oxidation number increase, the element is giving electrons. Electrons are transferred from the oxidized atom to the reduced atom.

If you find some mistake in my English, please let me know!

Order of filling levels and sublevels of electrons: 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²3f¹⁴5d¹⁰6p⁶for an element with 5 electrons in the 3d energy level: full configuration: 1s²2s²2p⁶3s²3p³.