Background information is very useful when narrowing down your topic, or when first learning about your topic. Background research (or pre-search!) is the first step in the research process. Getting background information on your topic allows you to learn enough about your topic to decide which specific aspect of that topic you wish to focus on, and gives you enough information about your topic for you to be able to talk about your topic for about a minute without repeating yourself.
The best way to complete background research is to use a reference book!