Brain vessels. Both are potential sources of brain bleed. Avm is an abnormal tangle of brain blood vessels connecting from artery to vein, aneurysm is an outpouching or bubble on an artery with a weak wall. Both can rupture. Both are treated by neurosurgeons or other cerebrovascular specialists. Sometimes an aneurysm can form on the feeder vessel of an avm.
Arteriovenous malfor. Avm=arteriovenous malformation. These are a tangle of vessels where there are "short circuits" of arteries directly feeding into the veins and thus bypassing the normal capillary bed. These are particularly well studied in the brain as are brain aneurysms which are about 10x more common. A brain aneurysm is like a balloon off of an artery that can rupture with devastating consequences.
Blood vessels. Arterio-venous malformations involve congenital anomalies and connections. Sometimes the vessels will enlarge. Aneurysm is usually arterial, rarely congenital, and usually later in life.
Avm. Arterio venous malformations can occur anywhere in the body and can present as bleeding . Aneurysms are weakness on a wall of a vessel like a artery and eventually can burst and cause bleeding. They to can be anywhere in the body.