communicate是动词，含义为交流。
If you communicate with someone, you share or exchange information with them, for example by speaking, writing, or using equipment. You can also say that two people communicate.
如果你与某人沟通（communicate），你与他们分享或交换信息，例如说，写，或使用设备。你也可以说两个人交流（communicate）。
例1：
My birth mother has never communicated with me.
我的生母从未与我交流过。
例2：
Officials of the CIA depend heavily on e-mail to communicate with each other.
中情局的官员们很大程度上靠电子邮件相互交流。
而exchange含义是交流时，是作名词。
An exchange is an arrangement in which people from two different countries visit each other's country, to strengthen links between them.
交流（exchange）是指两个不同国家的人互相访问对方的国家，以加强他们之间的联系。
例：
...a series of sporting and cultural exchanges with Seoul.
…与首尔的一系列体育和文化交流。
exchange作动词时，含义为交换。
If two or more people exchange things of a particular kind, they give them to each other at the same time.
如果两个或两个以上的人交换（exchange）某种特定的东西，他们在同一时间给对方。
例1：
We exchanged addresses.
我们交换了地址。
例2：
The two men exchanged glances.
那两个人交换了眼神。