Understanding the Elusive Concept of "Res Judicata" in Family Law

Ab kuchh to clear karo, friends. Textbook mein kaha jata hai ki Res Judicata aisa rule hai jiska matlab hai ki ek case court mein suvidhaa se nipla jaa sakta hai agar usmein vaidhanik samasya aadi solve ho chuke hain. Par kya yeh aisa lagta hai ki inki practical application mein koi zikr nahin hai. Mera internship mein dekhaa, do minute mein case dismiss ho gaya. Agar aapko bhi yeh samasya aayi hai, to please share kijiyega ki aapne AP LAWCET ka exam aisa kaise pass kiya.

Res Judicata ka kya ek vishesh example ya definition hai jo main isse samjha sakta hoon?