Member States shall ensure that the storing of information, or the gaining of access to information already stored, in the terminal equipment of a subscriber or user is only allowed on condition that the subscriber or user concerned has given his or her consent, having been provided with clear and comprehensive information… about the purposes of the processing.
There are already a lot of sites discussing and explaining the European directive like Information Commissioner’s Office (ICO) and All About Cookies. You can find tons of information on them like the difference between session- and persistent cookies. Apart from the distinction between session and persistent cookies, cookies can also be separated into functional and non-functional cookies. Functional cookies are cookies that are required for the basic operation of your application – most of the time these are also session cookies. Non-functional cookies however are not required for your application to work properly, they are additional and most of the time they only provide an added value for the applications owner. It’s on these last kind of cookies the directive applies. The EU Member States all have their own legislations derived from the EU Directive, they all are slightly divergent amongst themselves.