Contract vs. Constitutional Contract - Kaunsa hai yeh?

Maine socha tha mujhe Constitution, Contract, aur Constitutional Contract ka difference pata hai, lekin abhi tak samajh nahi aaya. Maine kuch notes dekhe hain jahaan likha hai ki Constitutional Contract Constitution mein mention kiya hua Contract hai jismein State aur citizen ke beech agreement hota hai. Lekin phir Contract ka kya matlab hai? Constitution mein to yeh likha hai ki State aur citizen ke beech agreement ko Contract ke naam se khaa jaa sakta hai, aur phir bhi yeh Constitutional Contract aata hai. Maine suna hai ki Constitution Contract ke baare mein kuch special rules banata hai jo Civil Contract se alag hote hain. Please help, yaar!