Beating the wife

I'm not a muslim nor part of any other religion. But the question about muslims being allowed to beat their wives is really troubling me for some time now. You hear so many different things about it and i would love to have someone with knowledge explain it to me. A lot of muslims deny or eventually agree its allowed but only very lightly with an small "arab toothbrush" (sorry dont know how its called). On the other hand if heard from islam critiques that in the time of mohammed all of his companions have beaten their wives and that there are hadiths about a girl coming to Aisha being green and yellow from all the bruises of being beaten.

So what is actually the truth about it? I cant imagine you can beat someone severly with a toothbrush and how does all this play Out in reality? Like is It common that a muslim husband would literally pull Out a toothbrush when the wife is "misbehaving"?