Reduction and oxidation are often called redox for short. For carbon, we can often determine the oxidation state by counting the number of bonds from a carbon to oxygen or another heteroatom.
In the table, the first column (the most reduced form of carbon) has zero bonds to oxygen. The last column is the most oxidized form, carbon dioxide, with four bonds to two oxygens.

Alkenes and alkynes do not even have a heteroatom and so their equivalence comes from the kind of interconversions they undergo. Reduction reactions take functional groups and move them a column to the left; oxidation move a functional group to another functional group that appear in a column to the right.