Charles Townshend is by far best known for his policies towards the American colonies that helped lead to the Revolutionary War. These were made while he was President of the Board of Trade and later while he was Chancellor of the Exchequer.
Basically, Townshend decided that it would make a lot of sense to impose various taxes on the colonies to help defray the costs of the Seven Year War. Townshend and others felt that the British had borne the costs of the war while the colonists had gotten the benefits.
Because of this, he supported taxes such as the very unpopular Stamp Tax. After this was repealed, he imposed a variety of taxes in a law now known as the Townshend Acts. These taxes helped to make the colonists very angry about British rule and eventually led to them rebelling against England.