They had soon formed a firm friendship.是什么意思？

They had soon formed a firm friendship.

他们很快结成牢固的友谊。

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。

had

v. 有（ have的过去式和过去分词 ），（亲属关系中）接受，拿，买到；

例句
He claimed that his parents had abandoned him...
他声称父母遗弃了他。

soon

adv. 立刻，马上，一会儿，不久，快，宁愿；

例句
The minister advised him to leave as soon as possible...
部长建议他尽快离开。

formed

adj. 成形的，成形加工的；v. 形成，构成，产生( form的过去式和过去分词 )，是，（使）成形，结成（友谊）；

例句
A frown formed between her arched brows.
她皱起两道弯眉。

firm

adj. 坚固的，坚牢的，坚定的，坚决的，严格的，确定的；vt.& vi. 使坚固，使坚实；n. 商号，商行，公司，企业，工作集体；adv. 坚定地，稳固地；vt. 使坚定，使牢固；vi. 变坚实，变稳固；

例句
...the accounting firm of Leventhal & Horwath.
利文撒尔-霍瓦特会计师事务所

friendship

n. 友情，友谊，友善的关系，友善，好意；

例句
Nothing cements a friendship between countries so much as trade.
贸易最能增强国家间的友谊。