First of all, let's break the word balun in two. Bal - un. Go one step further and we have: balanced - unbalanced. Bal - un. get it? Balanced to unbalanced. Basically, a balun is a transformer. A one to one balun (1:1) transforms, for example, a 50 ohm balanced feed point on an aerial to 50 ohm unbalanced coax. The impedance ratio of such a balun is one to one. A 6:1 balun? 300 ohm to 50 ohm. Even I can work that out - 300 divided by 6. An impedance ratio of 6:1 It's easy to throw the word balun around when talking about aerials. But it seems to me that is some confusion here.
One of my gripes is companies who advertise balanced aerial tuning units when they're not balanced at all. A simple L-match unit with a 4:1 balun wired across the aerial input terminals is NOT a balanced ATU. Apart from that, the correct term is AMU - aerial matching unit. OK, I'll stop moaning.
I don't like baluns. When operated in mismatched situations, they become extremely lossy. If dealing with high voltages, they catch fire. Unless wound with thick enough wire, they burn up with heavy currents. Baluns are expected to work over a vast range of frequencies and deal with a tremendous range of impedances. Unless very well designed and built, they can't do it.