What is the meaning of “quasi-judicial body”

Explaining the meaning of quasi-judicial body Civil Appeal arising out of SLP (C) No. 23127 of 2018 Page 21 of 27 in Indian National Congress (I) vs. Institute of Social Welfare & Ors.3 , it was held that-

When any body of persons has a legal authority to determine questions affecting the rights of subjects and a duty to act judicially, such body of persons constitute a quasi-judicial body and decision given by them is a quasi-judicial decision. It would also be a quasi-judicial order if the statute empowers an authority to decide the lis not between the two contesting parties but also when the decision prejudicially affects the subject as against the authority, provided that the authority is required by the statute to act judicially. Further, what differentiates an administrative act from the quasi-judicial act is that a quasijudicial body is required to make an enquiry before arriving at a conclusion. In addition, an administrative authority is the one which is dictated by policy and expediency whereas a quasi-judicial authority is required to act according to the rules.

Question of Res Judicata: 

Supreme Court in Shrimati Ujjambai vs. State of Uttar Pradesh & Anr[AIR 1962 SC 1621] has held that the principles of res judicata equally apply to quasi-judicial bodies. Whenever a judicial or quasi-judicial Tribunal gives a finding on law or fact, its findings cannot be impeached collaterally or in a second round and are binding until reversed in appeal or by way of writ proceedings. The characteristic attribute of a judicial act or decision is that it binds, whether right or wrong. Thus, any error, either of fact or law, committed by such bodies cannot be controverted otherwise by way of an appeal or a writ unless the erroneous determination relates to the jurisdictional matter of that body