Distinction between 'Constructive Dismissal' and 'Retrospective Effect of Resignation'

Maine CLAT PG k preparation ki thi aur mujhe yeh do concepts bilkul confused kardiye hain. Maine socha, kya aap log bhi pata chaleinge? Constructive Dismissal, Resignation aur Retrospective Effect of Resignation yeh saare cheezein ek dusre se judi hui hain. Pehle to hum log jaante hain ki jab employee ko company ne tenure se bina notice diya ke job se nikala hai, toh vah constructive dismissal ka maamla hai. Lekin, yeh bhi aata hai ki jab employee ne resignation di hai, iska effect retrospective ho sakta hai. To, kya voh bhi kuch samajhe?