The four macro skills of communication are as follows:
Speaking is obviously one of the most direct and useful forms of communication. However two people can speak to each other yet still not be able to communicate anything - they could be speaking different languages. Speaking is used mainly when people are face to face, but it can also be over the phone and now over technology such as webcams and video calling.
Listening is of course closely related to speaking and there cannot really be one without the other if it is to be a successful communication. Listening enables a person to soak in any information that is given to them; in turn the information can be passed on to another party later on.
Reading is another important skill in communication. In the past, books and newspapers were the most commonly read items; now emails and text messages form a lot of a normal day's communication activities.
Writing is closely linked with reading as, like speaking and listening, they really work in harmony to ensure successful communication. Again language can be a potential barrier with writing.