It essentially means "the act or process of" or "the state or condition of being".
Here are some examples:
* Develop (verb) -> Development (noun) - the process of growth or change
* Improve (verb) -> Improvement (noun) - the process of making something better
* Manage (verb) -> Management (noun) - the process of controlling or directing something
* Move (verb) -> Movement (noun) - the process of changing position
So, "development" signifies the process or result of something growing, evolving, or becoming more complex.