Doubt: Primary vs Secondary Evidence - kya hua difference?

Yaar samajh nahi aaya, please help. I've read the notes and chapters multiple times but still confused between primary and secondary evidence in the Evidence Act. Agar koi ek ek example de de toh samajh aayega, lekin mere pass lagta hai dono hain ek jaise hi. Primary evidence hai jo direct source hai, jaise ki aadhaar documents ya witness statements. Secondary evidence is kya, secondary kya mante hain yeh toh samajh nahi aaya. Agar primary mein ek paper document hai, toh secondary evidence ki koi limitation hain ki woh bhi ek paper document hi hona chahiye? Kya woh electronic form mein bhi ho sakta hai?