Unsaturated hydrocarbons are organic compounds containing carbon-carbon double (\( C=C \)) or triple (\( C \equiv C \)) bonds. They are classified into alkenes (containing double bonds) and alkynes (containing triple bonds). Unsaturated hydrocarbons are more reactive than saturated hydrocarbons due to the presence of multiple bonds.
Example:
\[
\text{Ethene} (C_2H_4), \text{Ethyne} (C_2H_2)
\]