DM stands for District Magistrate.
He is an Indian Administrative Service (IAS) officer who is the senior most executive magistrate and chief in charge of general administration of a district in India.
The activities of the district administration practically covers a wide range and touches almost at every level the loves and activities of the people.
The main task of the district administration is as such to implement programs with the active co-operation and support of the people of the district.
SDM stands for Sub Divisional Magistrate.
A district is divided into subdivisions. Each subdivision is headed by an SDM who enjoys the powers of an Executive Magistrate and Collector.
He performs various magisterial tasks under Criminal Procedure Code 1973 and several other minor acts
An SDM can be a junior member of the Indian Administrative Service or a senior member of the State Civil Services with relevant experience in subordinate positions.
All subdivisions (tehsils) are under the charge of SDM (Sub Divisional Magistrate). He has direct control over Tahsildars of his subdivision and serves as a channel of correspondence between the District Officer of the District and Tahsildars of his subdivision.