Greaseproof paper comes in sheets or rolls; it always used to be used for wrapping
cheese,
meat and other fatty food for storing in the fridge (or
larder) in the days before
Clingfilm. Indeed many recommend it for this purpose because it allows the meat to 'breathe' and does not impart any fat-soluble
plasticisers into the product.
It is a glazed paper (27 - 45 gsm), coated to prevent grease absorption. It is similar in texture to parchment paper but it is not non-stick. Older cookery books often tell you to line baking tins with greased greaseproof paper, which may sound a little odd. The reason for greasing it is partly to help it peel off the baked cake, and partly to help it stick to the tin during the process of lining (anyone who has tried to line a tin wthout greasing it will know just how much the stuff slides around!).
Greaseproof paper can be used to wrap or cover food which is to be steamed (such as fish or chicken), or baked in the oven. It helps to keep the food moist but still allows the passage of steam.