They travel to and fro between London and Paris.是什么意思？

They travel to and fro between London and Paris.

他们奔走于伦敦和巴黎之间.

they

pron. 他/她/它们，人们，大家，政府，当局，她们；

例句
The storms had abated by the time they rounded Cape Horn.
他们绕过合恩角时，暴风雨已经减弱。

travel

n. 旅行，进行，移动，漫游；vi. 旅行，传送，前进，行进，[篮球]走步；vt. 经过，通过，游历；

例句
It is generally not advisable for expectant mothers to travel by air after the 28th week of pregnancy.
怀孕28周以后的准妈妈一般不宜乘坐飞机出行。

to

prep. 向，朝着，到，关于，属于；adv. 朝一个方向的，到某种状态，关闭；

例句
I suggest you leave it to an expert...
我建议你把它留给专家来解决。

and

conj. 和，与，而且，于是，然后，因此；

例句
I spend a lot on expensive jewelry and clothing...
我花很多钱购买昂贵的首饰和衣服。

fro

adv. 向那边，向后；prep. 〈英方〉

例句
The boat was rocking gently to and fro in the water.
小船在水中轻轻地来回摇荡。

between

prep. 在…之间，私下，暗中，在…中任择其一，来往于…之间；adv. 当中，中间；

例句
How big is the abyss between what you think you are and what you actually are?
你对自己的认识和真实的你之间差别到底有多大？

London

n. 伦敦（英国首都）；

例句
Lord Salisbury bought the picture at auction in London some years ago...
几年前，索尔兹伯里勋爵在伦敦拍得了这幅画。

Paris

n. 巴黎；

例句
The dramatic World Motor Sports Council meeting in Paris blew the championship wide open as Schumacher was also docked six points...
在巴黎召开的令人瞩目的世界汽车运动理事会会议使冠军归属充满各种可能，因为舒马赫也被扣了6分。