Oral language is significantly different from written language. Often times, written words are best for your eyes, and oral words are best for your ears.
Here are important aspects of these two different vary different ways we use language.
Age
We have had oral communication since the beginning of human history. The written word came later, approx. 3100 BC, invented by the Sumerians.
Learning
Most people experience that they first learn to hear and speak, and afterwards they learn how to read and write.
Learning to hear and speak is considered innate and not something you have to learn, and you start with oral communication early in life, usually within 2 years of age.
Structure
Speech consists of basic units: “Phonemes” or sound units, with no meaning in themselves. When these are combined it is called “morphemes” and these have meaning. For example, we can combine the phonemes “s”, “i”, “m” and “p” and “l” as “simple”. Alphabetical scripts work that way.
In some languages, each syllable refers to an oral syllable or sound; Japanese is a typical example. In so-called logographic scripts such as Chinese, each character stands for a whole word.
Remember or lookup
The first recordings in history can be traced back to around 1860, but it was not until after World War II that recordings on magnetic tapes became widely available. Before that, speech could only be remembered or written down.
The written word, on the other hand, has been preserved from its inception, thousands of years ago. This property laid the foundation for dictionaries, schedules, stories and libraries … the basis of our civilization.
Standardization
Oral language has dialects, that is: variants across geographical areas and social groups. Written language, on the other hand, benefits from uniformity, supported by state and educational institutions.
Changes
Oral language consists of a combination of characteristics such as tone, speed, pitch, etc. which is not only unique to each individual, but which is also not constant but is constantly changing. As a whole, oral language is constantly changing, with many subtle changes that sometimes can be very hard to notice or measure.
Changes in written language, due to standardization, prestige etc. takes much longer to change. The first paragraph of the constitution is written in a way we no longer write, for example. But it for sure is unlike the way people speak, and as such a good example of the changes and differences between the written and the spoken word.
Recipient
Before recording and vlogging became commonplace, it was easier to identify and relate to the recipient. One of the basic characteristics of a dialogue is that there is room to elaborate on certain statements where needed, so that communication is effective and tailored.
Written messages via e.g. email can easily be misinterpreted when the message is forwarded (to yet other recipients who easily might lack knowledge of the context).
Characteristics of spoken and written language
When speaking, there are many parameters that are set, such as repetition, intonation, speed, dynamics, pressure, rhythm, pauses, etc.
The choice of words is usually simpler and grammatical rules are not as important as in written language.
In written language, one can often recognize that the text has been reviewed several times, before the author was satisfied with the latest version (this sentence is an example, by the way). It is an iterative process and an attempt to communicate as clearly as possible. The content also has a different density of information as the reader can absorb the information on their own terms. The structure of the text is consciously constructed.
Another aspect is that one has to be careful with grammatical rules and punctuation. Written language is thus much more thoughtful than speech.
Consequences
When you are aware of these aspects of oral and written language, it has some consequences, e.g. you may wonder how effective audiobooks really are as an alternative for Dyslexics.
It may also be obvious that a telephone call is much more efficient than an email. You can more easily adapt to the recipient and changes are often made in several dimensions: you adapt everything from speed, tone of voice, word choice and sentence length in an instant, and as you get feedback, you can adapt even as you communicate. A printed speech cannot be changed, once submitted.