The division of power between legislative, executive and juridical powers is relevant to understand decison making at ay scale of government in democratic settings, reaching from the local level up to the supranational level. Development and preparing and executing projects is done by the executive power; the legislative and juridical powers are the contextual powers in this system. The exact configuration varies by country.

For extensive further reading on the topic of division between legislative, executive and juridical powers in the public domain:

http://en.wikipedia.org/wiki/Separation_of_powers