Road maps enable you to plan from point a to point b, showing all the different places you have to pass to get from the starting point to the end point of your journey.
Organizational objectives are similar in that they chart the objectives that an organization, such as a business, has to put in place to ensure that they achieve their end goals. Whatever those end goals may be.
The analogy could be that of an actual map for physical roads...
Imagine you are going on a trip, driving across Europe with friends.You no doubt know where you want to visit and what you want to see.
However there's also the slightly less-exciting, but nonetheless important details to figure out... such as how much money you have to spend on things such as food, then there are the places you are going to need to stop and spend the night... so you need to think about hotels etc using your map. Plan a route.
An organization working on a financial project, for example, has to plan out how it's going to reach it's desired result, such as generating further business.
The organization has to plan steps such as how many staff hours will need to be allocated to the project, maybe they need to implement a social media strategy, what's their contingency plan? Who is accountable for which part of the project?
The main similarity between an organizational objective such as that mentioned above and a road map is that both enable you to plan forward, to predict in way how you will reach your end goal or destination.