For example look at this:
http://www.amazon.co.uk/Faces-Babys-...7862966&sr=8-1
You will see it says:
"In stock.
Dispatched from and sold by Amazon.co.uk. Gift-wrap available. "
If it says dispatched from another company than amazon, it is their marketplace.
Also the "21 new from £1.28 3 used from £1.31 " are all marketplace sellers. Not amazon direct.
If you wish to see the marketplace sellers feedback. Just click "new" or "used" and you can see all sellers and click their feedback ratings.
Peace