They are hydrocarbons which are joined by single bonds only. Thus called as saturated hydrocarbons. The general formula is CnH2n+2. Some examples are Methane-CH4 Ethane- C2H6 etc.
They are joined by at least one double bond between them. They are reactive in nature and are called unsaturated hydrocarbons. Their general formula (not including cyclic compound) is CnH2n. Examples are Ethene- C2H4, Propene-C3H6 etc.
They are the hydrocarbons that are formed when one hydrogen molecule is removed from the alkane . Methyl-CH3, Ethyl-C2H5 are some examples.
They are unsaturated hydrocarbons which are having at least one triple bond between them. Ethyne-C2H2 and Propyne-C3H4 are the examples of alkyne.