What are polyhalogen compounds? Give examples.

Organic compounds containing more than one halogen atom are known as polyhalogen compounds.
Examples of some polyhalogen compounds are:
$(i)$ Dichloromethane $(CH_{2}Cl_{2})$
$(ii)$ Trichloromethane/Chloroform $(CHCl_{3})$
$(iii)$ Triiodomethane/Iodoform $(CHI_{3})$
$(iv)$ Tetrachloromethane/Carbon tetrachloride $(CCl_{4})$
$(v)$ Freons (chlorofluorocarbons of methane and ethane),Freon-$12$ $(CCl_{2}F_{2})$
$(vi)$ $p,p'-$Dichlorodiphenyltrichloroethane $(DDT)$,$CCl_{3}CH(p-C_{6}H_{4}Cl)_{2}$