The hydrocarbon in which all the valencies of all the carbon atoms are satisfied only by single bonds, is known as an alkane.
e.g. Methane (CH₄), Ethane (C₂H₆)

The unsaturated hydrocarbon containing a carbon-carbon double bond, is known as an alkene.
e.g. Ethene (CH₂ = CH₂)

The unsaturated hydrocarbon containing a carbon-carbon triple bond, is known as an alkyne.
e.g. Ethene (CH₂ ≡ CH₂)