It's when an artery wall weakens or weakens and balloons. They can occur all through the body, but the famous ones are the brain aneurysms. We can have them at any point in our lives; even be born with them. There are symptoms, but they depend on where the aneurysm is located. Unexplained weakness, low blood pressure, fast heartbeats/rates are all indicators of that...and many other things. Death comes from ruptured aneurysms. You basically bleedout internally faster than anyone can get in there to repair the rupture, since it only takes a minute or two for all your blood to be pumped out.