Answering this question seems like it should be as short as a simple definition. According to Dictionary.com, litigation is simply "1. the act or process of litigating or 2. a lawsuit."
While those definitions are accurate, they don't actually tell you anything. Filing a lawsuit triggers a series of mechanisms that help the parties work towards resolving a dispute. While many people assume that lawsuits are always resolved before a jury or a judge in court, they are commonly settled by a out-of-court agreement between the parties involved thanks to the litigation process.