"there aren't any seats" and so she has to stand, and she stands by "holding onto a handrail," "handrail," (one word). “没有座位”，所以她不得不站着，“抓住扶手(handrail)”站着。

A handrail is a piece of metal that is in a subway train that you can grab onto. 扶手是一块金属，在地铁里你可以抓着它。

You can hold your hand around this piece of metal so that you don't fall when the train goes forward and stops; 你可以抓住这块金属，这样当列车发动和停下的时候你就不会摔倒；

this is called a handrail because it's where you put your hand. 这叫做扶手，因为你的手扶在了上面。

Of course, you could also put your hand on the person next to you, but they may not like that, so use the handrail! 当然，你也可以把你的手放在你旁边的人身上，但他们可能不喜欢，所以用扶手吧!