Cookies are small files that contain information useful to a web site -- such as password, preferences, last date visited, etc. You may remove the cookies that you don't want adn since some of them are a privacy issue, many people remove them all.

Cache is just a collection of data downloaded to help display a web page. After you leave a site, much of the cache is left on your computer and is no longer needed. You can always remove the cache because it will be replaced as needed.

I thank you for clearing my doubts but it will be better if you clarify further , is it good for me to clear cache before I exit net , if I remove cache, will my home page and bookmarks will be removed , please let me know ?.

You can see the current cache usage here and on the about:cache page, the latter can be opened via the location bar like a web page.

• Tools > Options > Advanced > Network > Offline Storage (Cache)

Clearing the cache only affects the copy of websites stored on your hard drive in the cache folder and doesn't affect other data like bookmarks.
If you clear the disk cache then Firefox needs to fetch a new copy from the server on a next visit.

See also:

• http://en.wikipedia.org/wiki/HTTP_cookie

Why some websites after their url write cached for example www.xyz cached . Please let me know why they added the word cached ?