What for sure is a aneurysm. And do they always kill u?

Not always fatal. An aneurysm is a bubble in an artery - the blood vessels going away from the heart. When part of the artery wall gets damaged and becomes thinner, the artery can blow up like a balloon. This balloon is the aneurysm. If the aneurysm bursts it can cause a stroke or bleeding to death depending on location. If caught before rupture they can be repaired. If they burst emergency surgery is required.
Where is it? Regardles of location, repair and cardiovascular risk control is the treatment. An aneurysm is a dilatation of a blood vessel to the point that it may leak blood and death from bleeding can occur. Sometimes sudden clotting and occlusion of the blood vessel occ. So you need to know which artery has the aneurysm and the size. For example, popliteal artery aneurysms clot off and you may get limb loss.