For many, the objectives behind the notion of “external communication” are rather explicit. It is a question of promoting the company’s image by all means possible to its external partners: customers, suppliers, media, governmental institutions, shareholders, etc.
On the other hand, the notion of “internal communication” is often less clear to the majority of people. We can however fairly simply summarise the concept by saying: It is a question of promoting the image of the company to its internal partners: the employees.
All employees, at every level of the company, have to understand and be mobilised around a common project (the company strategy). The marketing and the sales cannot be successful if the strategy they wish to deploy with customers and/or prospects is not clear. Meanwhile, human resources cannot effectively attract and retain talent if the perspectives are vague.
Lastly, your employees are the best spokespeople for your company among external partners (this is all the more true with the development of social networks). It is they who convey the best the image of your company to the media, possible customers, candidates for recruitment, etc.
This is why the notion of internal communication cannot be separated by that of external communication. An employee who reads in a special-interest publication that the financial performances of his company are worrisome has cause to be concerned if has not received any communication about it in house!