Cache is data that is usually saved in RAM or on a place on your disk that provides quicker access to previously accessed resources. The main use for a web browser is to cache a website the first time you access it, this makes any future access to that site faster by having a piece of it on your local disk or RAM. A search cache is usually a log of your previous searches so when you start typing, it suggests things in the drop-down box of what you might be searching for, so you don't have to type out the whole search string.