Were they?
Im guessing they were real but most stuff attributed to them is myth.
Yes, they were real. They inhabited a place in the Caucasus. However, the historic accounts (e.g. lopping off a breast to make it easier to draw a bow) were probably exaggerated by the Roman historians.
There may be a kernel of truth to the stories, but probably not more than that. There were any number of tribes from northern and eastern Europe and the steppes of Asia in which some of the women fought alongside the men, especially before the women married and had children.
The notion that they cut off or burned off their breasts in order to fire a bow more efficiently is probably the result of a case of ancient Greek folk etymology. The Greeks seemed to assume the name was from the Greek roots a- (“without”) and mazos- (“breast”). No one is really sure what the name means, it’s probably not that. At any rate, modern women seem to have no trouble firing a bow without resorting to self-mutilation.
The Amazons were supposed to live in Scythia, a region north and east of the Black Sea, and to live in a society without men. Any male children born were killed or sent to live with their fathers. The Amazon River was named after a tribe of female warriors supposedly found along its banks by an early explorer, Francisco de Orellana.
Greek reverence for the human form probably had something to do with it as well. The idea of physical self-mutillation was horrifying to the Greeks, and attributing such behavior to real or mythical enemies (the Amazons did legendarily go to war against the Greeks) was one way of discrediting them.