Written communication aims to inform someone of something in a way that they are able to read and understand the message, with an intention of responding to it. In some cases the only way you can communicate certain information is via written communication. This could be the case in certain aspects of a job, such as a statement of an incident and so on. You could also consider that story telling in novels is a way of written communication because even though the words are fictitious they are still communicating a particular narrative.
What makes it coherent?
If a form of written communication cannot be understood by the recipient then the message may well as not exist. In order to write a piece of information that can be understood clearly you need to have the correct spelling, punctuation and grammar. In addition, depending on the form of written communication you need to make sure you use the right format. For example, if you are writing a letter you need to ensure you are using the appropriate format.
Why?
Written communication is prevalent in everyday life because it is not simply the case of writing down a message on a piece of paper. Nowadays we use written communication constantly in the form of email, text messages, online chats, social networking and so on. It has become an integral part of communicating with people around us.
Sometimes people can communicate more better with written communication than to actually talk to someone over the phone or talk to someone in person Sometime people with high anxiety can only commuincate with written communication Also written commmunication helps you to write down your thoughts and how you feel about things