Representation is how things are portrayed in the media.
Groups of people (Social groups, determined by many factors, like gender, ethnicity and age)
Issues (Specific topics, such as climate change, knife crime, drug abuse, and the economy.)
Events (Things that happen, such as an election, royal wedding, flood or terrorist attack.)
We can credit this idea, that different media products produce differing representations, to Stuart Hall, who wrote an entire book entitled Representation.
So, Fox News and right-wing media represent Trump positively, while The New York Times and left-wing media represent him negatively.
The same can be applied based on age, race, gender, etc.
A lack of diversity among media producers tends to result in under-representation or misrepresentation of other social groups – women, the disabled, ethnic minorities, and people below or older than working age.
The media industries are increasingly diverse and thus tend to represent a broader range of social groups in a more positive. Still, therefore remain areas of the media in which minority groups are under-represented.

Here, the mid-shot makes Trump prominent in the shot. His expression and hand gesture connote intelligent consideration. The appearance of another person in the background helps to imply Trump’s power and the idea that others support him and defer to him.
In this shot, the audience is positioned to respect Trump. It constructs a positive representation. A media producer would select this to create a positive view of Trump or to appeal to an audience it expects to approve of Trump.
Here, the small desk, long shot and high angle (looking down slightly at him) make Trump look small, even childish, and the lack of anyone around him may make him seem isolated. He’s been photographed in the middle of speaking, which makes him look more awkward and less dignified. He’s surrounded by the iconography of the USA (flags, emblem on desk) but, because of the other factors, these only give the impression that he is trying to be taken seriously – but failing.
In this shot, the audience is positioned to mock or criticise Trump. It constructs a negative representation. A media producer would select this to create a negative view of Trump or to appeal to an audience it expects to disapprove of Trump.