Giving up a claim or a right that can be lawfully exercised. However, there can be no waiver of a fundamental right.
A writ is a direction that the Court issues, which is to be obeyed by the authority/person to whom it is issued.
A petition seeking issuance of a writ is a writ petition. Pits in the first instance in the High Courts and the Supreme Court are writ petitions.
A writ of habeas corpus is issued to an authority or person to produce in court a person who is either missing or kept in illegal custody. Where the detention is found to be without authority of law, the Court may order compensation to the person illegally detained.
A writ of mandamus is a direction to an authority to either do or refrain from doing a particular act. For instance, a writ to the Pollution Control Board to strictly enforce the Pollution Control Acts. For a mandamus to be issued, it must be shown:
a) That the authority was under obligation, statutory or otherwise to act in a particular manner;
b) that the said authority failed in performing such obligation;
c) that such failure has resulted in some specific violation of a fundamental right of either the petitioner or an indeterminate class of persons.
A writ of certiorari is a direction to an authority to produce before the Court the records on the basis of which a decision under challenge in the writ petition has been taken. By looking into those records, the Court will examine whether the authority applied its mind to the relevant materials before it took the decision. If the Court finds that no reasonable person could come to the decision in question, it will set aside (quash) that decision and give a further direction to the authority to consider the matter afresh.
For instance, the permission given by an authority to operate a distillery next to a school can be challenged by filing a petition asking for a writ of certiorari.
A writ of prohibition issues to prevent a judicial authority subordinate to the High Court from exercising jurisdiction over a matter pending before it. This could be on the ground that the authority lacks jurisdiction and further that prejudice would be caused if the authority proceeds to decide the matter. Where the authority is found to be biased and refuses to rescue, a writ of prohibition may issue.
A petition seeking a writ of quo warranto questions the legal basis and authority of a person appointed to public office. For instance, the appointment of a member of a Public Service Commission not qualified to hold the post can be questioned by a writ of quo warranto and appointment nullified if found to be illegal.
These apart, a writ petition could seek other writs, orders and directions which the Court may fashion in response to the facts placed before it.