It's the difference between "how?" and "what?". A procedural approach describe the step you do something. But not what is the problem you want to solve and why you want to do this to solve it. A declarative approach on the other end, describe the goal and intended solution first and try to make a proper procedure to achieve the goal.
The two approach have their own cons and pros. But aren't explicitly exclusive. Sometimes the goal and solution aren't that clear. So you do it procedurally until you find a POC(Proof of concepts) that may actually solve the problem. And refine it in a declarative way.
The two approach have their own cons and pros. But aren't explicitly exclusive. Sometimes the goal and solution aren't that clear. So you do it procedurally until you find a POC(Proof of concepts) that may actually solve the problem. And refine it in a declarative way.