many people can't have their rights enforced by the courts because they are too poor to bear the cost or are not educated enough to know their rights or are otherwise disadvantaged. when the rights of such people are violated, any person or organisation can file a petition for redress in a high court or the supreme court. such a petition may also be filed in the public interest to make a government perform a public duty or when something like environmental pollution harms or threatens to harm the people. the process of making or defending a claim in a court of law is called litigation. Litigation for protecting public interest is calledPublic Interest Litigation(PIL).
A PIL is different from other litigation in that it is not necessary for the affected people to themselves file the petition for starting legal proceedings. anyone acting in the public interest may do so. A PIL is also simpler to file than other cases. Even a letter explaining the facts can be recognised as a PIL. The court may take itself take notice of a wrong done to public and act on its own.