In the world of software programming phraseology imperative and declarative are two variations of programming techniques. Not specific to object oriented programming, however it’s often associated very closely to object modelling.
Fundamentally declarative programming is when you describe or declare a method or function to perform a specific task without giving the function how to achieve the end outcome. You only provide the method how to achieve the final outcome, not the process and steps that’s required in order to achieve the end result.
Imperative is on the other side of the scale. You provide the function with detailed logic on how to achieve the final out come, what route(no network pun intended) to take and what assumptions to make in order to the achieve.