A creamer is a vessel for holding milk or cream for putting in your tea or coffee.  I wish i could offer you some advice on buying a creamer but I'm afraid the best I can do is say buy what you like.  Mine happens to be stainless steel but I suppose if you have china teacups and saucers it'd be worthwhile for you to have a creamer in a matching pattern.

A creamer could also be a disposable plastic cup of half and half with a litte paper lid.  A nice way to open these creamers without making a huge mess is to fold the little paper lip up over the top, and hold the creamer with the lip submerged in your coffee.  In a few seconds the glue will melt and you'll be able to gently squeeze the cream out of the creamer without getting it all over yourself and your companions.