The Separation of Powers conundrum is still killing me!

Tumhare paas 3 din hain aur main abhi bhi yeh ek cheez samaj nahi pa raha hoon. Judicial Review aur Executive powers ke beech ka difference kya hai? Mainne Hardayal Singh vs. State of U.P (1964) ka judgment padha hai, lekin yeh section 14 (1) ka interpretation hai jo mujhe pehchaan nahi a raha hai. "Subject to law made by parliament by law, the executive power of the Union extends to matters with respect to which the Union parliament has power to make laws." Yeh kya karta hai, bas? Executive powers ko kis extent tak hain? Kya yeh unke pass sab kuch hai ya nahi? Main to kya kar sakta hoon?