The term Yellow journalism is used to sensationalise a news over the facts of the situation. It is done in order to market a news and increase its circulation amongst the public.
It came into being when two big newspaper name in the new York, namely The World and The Journal caught themselves in a competition of whose news is sold the most. In order to do so, each name used different tactics to pop the news more into the eyes of the customer and see who sells most.
Now a days, it is very commonly seen in television news as well where each news is materialised according to the taste of the viewer.