Public international law (or the law of nations) is a body of customary or conventional rules which are considered as legal binding by civilized states in their intercourse with each other and is concerned solely with the rights and obligations of sovereign states.
Private international law (or the conflict of laws) may be defined as the rules voluntarily chosen by a given state for the decision of cases which have a ‘foreign’ element or complexion.
Thus, where two Englishmen make a contract in Portugal for the sale of goods situated in Lisbon, payment to be made in London, an English court would certainly recognize and apply Portuguese law as far as it affected the validity of the contract.
The private international law forms part of municipal laws of a state and is meant for purpose of deciding weather a given case involving “foreign’ element (i shall be adjudicated upon by its own domestic laws or by laws of some other state; and (ii) shall be subject of its courts of some other state.
Thus private international law deals with cases in which some relevant fact has a geographical connection with a foreign country and may on that ground raise a question as to the application of Indian or some other appropriate foreign law to they determination of the issue or as to the exercise of jurisdiction by Indian or foreign courts.
The public international law is concerned solely with rules concerning the rights and obligation of the states (i.e. countries) interest. Whereas, generally, speaking individuals and their dealings are the sole concerns of private international law.
Thus in the case of private international law, the disputes are of a private character ,though one of the dispute ,may be a sovereign state .Moreover ,unlike public international law, private international law of every state is different. Also there are as many systems of private international law as there are systems of municipal law, thus, we have rules of private international law in the fields of birth, marriage, divorce insolvency, wells contracts death and the like.