The Army Ranger and the Navy SEAL are two of the most iconic figures in our military culture. They are both Special Forces, drawn from different parts of the American military. The military itself has four branches: the Army, the Navy, the Air Force, and the Marines. They are each tasked with defending the homeland and carrying out operations to secure global security.
Not all of what they do is about war, either - they provide a huge amount of humanitarian aid, and when there are terrorists to be fought, they are often sent in. They also secure the high seas and the world's key trade routes against piracy. The world is a lot more dangerous for some people because of them, it's true - and many of those people are sadly innocent civilians - but it's also a lot safer for many, including not just Americans but also our allies and even some of our enemies. Even by current standards (i.e., civil war), it would be a particularly miserable day indeed in Yemen, for example, if the Gulf of Aden or the Red Sea were overrun by pirates!
Each military branch has its own special elite units to match its particular required skill set. If you tell us about your skills and preferences, we'll see which of these two elite fighting forces you should join - or whether you should stay at home instead!