Bikes are the most common means of transportation in our daily life, but have you ever noticed that a man's bike is quite different from a woman's bike? The traditional difference between a man's bike and a woman's bike is the top tube design. A man's bike would have a top tube going straight from the top of the head tube to the top of the seat tube, while a woman's bike would have a top tube that connected to the seat tube somewhere lower down. This was originally to make it possible to ride a bike while wearing a skirt without exposing any morally offending body parts while mounting the bike. A consequence of this is that traditional women's frames are weaker than men's, which is why performance-oriented bikes all look the same regardless of the gender of the rider.
If you're looking for a performance-based difference, then women often have shorter upper bodies and arms than men, so some manufacturers adapt to that by building frames with shorter top tubes. Others merely think a "cute" paint scheme (组合) on the smaller sizes of their standard frames will be called a woman's bike. Do note that the difference from one person to another can easily be bigger than the differences between the man's bike and the woman's bike standard. There are also a few other ways of fitting a bike to the rider. For example, handlebars can be replaced for some adjustments of riding position.
While it's nice to have a well-fitting bike, for an ordinary rider it's not as important for a MTB (山地车) as it is for a road bike. On a MTB the rider spends more time out of the saddle (鞍). While riding a road bike the rider spends more time on the saddle, so the position has to fit better. And if it's just for wandering around the block, then most riders would prefer a "woman's" bike. They will usually provide a more upright riding position, which is more comfortable for casual riding.
