Concepts of 'State' in Constitutional Law - Kya Fark Hai?

Main kabhi se pehle hi samajh nahi paaya hai, but abhi bhi main confused hoon. Kuch log kehate hain ki 'state' ki baat hai, to kya voh Bharat sarkar hai ya voh state government hai? Phir kuch log kehate hain ki 'state' ki baat hai, to voh vishesht roop se refer kar raha hai. To, kya difference hai? Main confused hoon ki 'state' ka kya matlab hai, Constitutional law mein. Kya yeh voh state government hai jo central govt ka part hai, ya voh vishesht state hai jo apne aap ka kaam karta hai? Aur kya lagu hai, Judicial Services ke liye?