They were smartly but casually dressed; possibly students...是什么意思？

They were smartly but casually dressed; possibly students...

他们衣着时尚，但很休闲，也许是学生。

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。

were

be的过去时复数和第二人称单数形式，有时代替 was,用于条件从句、动词 wish 之后等；

例句
Shops, houses, and vehicles were set ablaze.
店铺、房子和车辆全都陷于火海。

smartly

adv. 潇洒地，刺痛地，伶俐地，机敏地；

例句
He was a big man in his forties, smartly dressed in a suit and tie.
他是一个四十多岁的高大男子，穿西装打领带，看上去很精神。

but

conj. 但是，而是，除了，只因为；prep. 除…以外；adv. 只，不过，只是，另一方面；n. 借口，推辞，但是，反对；pron. [关系代词，意义相当于 who…not, which…not]；vt. 对…说“但是”；

例句
English food can be wonderful but the normal English diet is abominable.
英国也有美食，只是一般的日常饮食太过糟糕。

casually

adv. 偶然地，无意地，未经考虑地，漫不经心地；

例句
Johnson was clad casually in slacks and a light blue golf shirt.
约翰逊穿着休闲，宽松的长裤配淡蓝色高尔夫衬衫。

dressed

adj. 打扮好的，穿着衣服的，（畜、禽、鱼）剥皮（或去毛、鳞）、去内脏及分割加工好的，动词dress的过去式和过去分词；

例句
She was elegantly dressed with a double strand of pearls about her neck.
她着装典雅，搭配着一条双层珍珠项链。

possibly

adv. 可能地，也许，或许，敢是，容许；

例句
What could possibly disturb such tranquility?
什么有可能会破坏这样的宁静呢？

Students

n. 学生，大学生( student的名词复数 )，研究者，中学生；

例句
Part-time English classes are offered. In addition, students can take classes in word-processing and computing...
开设了非全日制的英语班。另外，学生可以修读文字处理和计算机课程。