The majority of knives sold in the UK nowadays are made of stainless steel. This also contains chromium which makes the knife rustproof but also makes it more difficult to sharpen. To overcome this problem stainless steel knives also include some carbon in their composition. So called ‘high carbon stainless steel knives’ are designed to give the user the best of both worlds, i.e. a rust proof knife which will not discolour but will also hold a good edge if it is regularly sharpened.
Carbon steel knives are a more traditional choice which have become less popular in recent years because they can rust and become stained. However because carbon steel is softer than stainless steel it can more easily be sharpened to a really good edge which will slice through food effortlessly. To avoid rusting, never put a carbon steel knife in the dishwasher. Wash it by hand, dry immediately, then store in a knife block or rack. Some people also like to just wipe the blade with a thin coating of oil prior to putting it away. This should not really be necessary so long as the knife is always kept clean and dry but if you do decide to use oil go for something neutral such as corn oil or canola oil. Olive oil is quite alkaline and should be avoided.