Men and women tend to think and act rather differently, taken as a group. Some of this is driven by biology, and some of it is driven by culture.
Whatever the causes of any particular differences, some of them will run counter to your expectations and instincts, causing you to make inaccurate predictions and assign wrong motivations. This can really bite you in the ass, so an understanding of where they're coming from will leave you much better prepared.
Upper body strength. This one is pure biology. We have a whole lot more of it than you do in the majority of cases, and our testosterone levels allow us to build muscle much more rapidly than you can. Unless you've had direct experience of this, you're very likely badly underestimating it. A man in the same percentile height and weight as you can not only pick you up, he can throw you. If he lifts on the regular, there's a chance he could damage a wall by throwing you at it.
Sense of smell: yours is a fair bit more sensitive than ours, especially where things like sweat and urine are concerned. We can walk past a piss-soaked alley and think it's a bit whiffy; you will walk past it, turn purple and choke. It's not bravado or grossness on our part, the smell is just much fainter to us.
Aggression, (Relatively) lots of testosterone means lots of aggressive impulses, Please note, however, that aggression and violence are two very different things. Violence is one way that aggression can be expressed, but it's certainly not the only way, If I had to give you a definition of aggression, I'd say "forcefully disruptive challenge". It's the urge to smash things, to jumpscare,to playfight and horse around, to let out a warcry and charge, to blow shit up, to run through a crowd of pigeons, to basically act like goats playing king of the castle in one way or another (headbutting a bonus).The presence of those urges is biological, the way we channel them is cultural. If you block off safe, sane outlets for this, then it will leak out less-desirable places. Don't distrust guys acting a bit goats-and-vikings; they're not dangerous monsters, they're channeling it responsibly. Worry instead about the ones with a temper, or no visible outlets at all.
Libido: we has it. Not that women don't, but on the whole it would seem that men are much, much more driven by it overall. Just look at the prostitution industry; the female customer base is incredibly tiny in comparison to the male customer base. Again, who knows how much of this is cultural and how much biological, but there are lots of issues leading off from it that I'll get to in a second.
Core elements of self-esteem: This is mostly cultural (though likely fed to some degree by a few biological tropisms), Men in our society are expected to project a certain image, and failing to do so will lose them the respect of their peers and make self-esteem hard to come by. Overcompensation and all kinds of shit can result - understanding the motivations can give you better insight into what's going on.
[continued next post]