Kya Contract Kya Hai, Sir?

Maine apne Contract Law notes padhne ki koshish ki hai, par yeh sab kuch toh thik se smajh nahi a raha. Kahan se Contract shuru hua, kahan tak hai, aur kaisa hua? Kuch log keh rahe hain ki Contract isiliye hota hai ki do people ka ek mutual agreement ho jata hai, jabki kuch log keh rahe hain ki contract sirf kuch specific terms ke bawjood hua hota hai. Aur phir yeh bhi hai, kya contract sirf written hi hota hai ya verbal bhi ho sakta hai? Main kafi confused hoon aur koi bhi bathe ki wajah batayein.