Probably the most popular means of messaging due to the vast number of people using the social networking site Facebook.
The language that is used on this application will be extremely casual, as it is generally used among friends to have informal conversations.
But due to the easy access of Facebook, many companies have pages promoting their services, users can easily message these companies. The example below is a message from me to a photography requesting to use one of his photos in my article, the language used is formal and the purpose of the message is made crystal clear.
This messaging service can also be used for casual conversations that rely on abbreviated words.
However, Skype offers a service “Skype for Business” which gives users the ability to have meetings in the form of messages as well as using a webcam. Of course, when employees are using Skype for Business they must use formal terminology avoiding slang completely.