Question

what are public interest groups ? how do they look after the public interests ? explain

Answer 1

Public Interest Groups refers to association of individuals or organizations formally organized on basis of one or more shared concerns trying to influence public policy in its favour. 
They form goals which could be a policy that exclusively benefits group members or one segment of society or a policy that advances a broader public purpose.
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Answer 2

Answer:

public interest group is a group that promotes the interests of the people of the society. There interests can be of a particular section of the society or of the entire society in general. Their activities benefit the entire society and not just a particular section of the society.