The "Basic Structure" Doomsday

Main problem hai yeh, 3 din bache hain aur Constitutionality of certain laws topic par mujhe basic structure ka concept thik se samajh mein nahin a rha hai, ya fir kuch aur. Sabhi to jaante hain ki basic structure kya hai aur kyon, phir bhi kaise koi Article 368 par amendments karne ka attempt karta hai, use Article 13 ka dhokha dete hue? Article 368 wala concept toh thik samajha hai, par kya basic structure ka definition hai, koi specific criteria hai ya fir yeh koi abstract concept hai? Aur phir yeh sab theek ho gaya hai, fir bhi Constitutionality test kaise hoga? Abhi to kuch samajh raha tha, phir se ek bhi baat yaad nahin a rahi hai.