1. of the general public, such as environmental issues OR
2. of some person/s who are unable to approach the courts directly, such as bonded labourers, prisoners, children etc.

PIL is generally initiated by filing “writ petitions” (petitions filed directly before the Supreme Court/High Courts to enforce fundamental rights). The Court may sometimes entertain even a letter or a newspaper report and treat it as PIL.

For further details, see Public Interest Litigation