There has been much written about this in the last two weeks.
See this link: http://www.autoexpress.co.uk/volkswagen/92893/vw-emissions-scandal-latest-news-on-the-dieselgate-recalls
Halfway down the page is an overall explanation of the scandal.
There are further links to help find out if your VW, Audi, Skoda or Seat is affected. In short, their 2009 onwards 1.6 and 2.0 diesels are likely to have these cheat devices built into the software.
There are likely to be recalls for these vehicles, although exactly what work will be carried out to them isn’t clear yet.
Be reassured though, if your car is affected, it is still safe, its fuel economy will not be affected and it will pass its MOT irrespective of this software.
If you have any concerns about your car, or you are planning to buy a second hand VW, Audi, Seat or Skoda diesel and are not sure what this may mean for you, please call me.
Petrol cars are not affected.