This is feedback generated from the audience for the show; this is not a selected group of people but anyone with a comment on the show. Whilst watching an episode of ‘Doctor Who’ many people send twitter and Facebook updates on what they think of the show. By monitoring the audience’s response to the episode it can help to improve future ones.
If for example many people comment on the way the Doctor dresses saying they really like it, the producers know to include this style of clothing in future episodes as it has had a good response. On the other hand if one of the characters are commonly spoken about saying they’re not funny and are generally not liked, then the producers will have to make a decision of what to do with the character. It may be the best option to replace the character or change the aspects that aren’t enjoyed.