Lets suppose any thriller stealing movie. Think what does robbers do before they hack the bank or anything else? They gather the information. They collect each and every information about bank system, alarm methodology, CCTV interface, Guards changing time, list of weapons having with guards.After gathering information they make plan and attack or rob the bank. You all are clever. So assume they don't have these much of information and they are going to rob bank directly, what will happen ? You will find them caught with by police.
Same scenario also applied in information security world. Before attacking or testing something a hacker/tester needs to find the information about his/her target. Now this target can be a network, web application, organization or a person. In our world finding information is also called as footprinting or doxing. Also the term reconnaissance can be used sometimes.
