In general Cookies fall into 4 categories:
Essential: Those which are needed for the normal running of the web site. An example of this type are ones which handle shopping baskets or remember where the user is on more complex sites.
Functional: Those which improve the functionality of the site but are not essential. An example of this may be remembering a particular setting such as the language in which the page is to be displayed.
Analytical: Those which benefit the site's owners. An example is the analytical cookies that count and track visitors, see which pages are the most popular and determine what the system capabilities of the user. The former help with determining what is popular and can help a site owner put more effort into the most popular sections of the site, the latter help in determining the best way to present information to the user (for example, is the audience primarily mobile or desktop). Knowing this information allows the site owner to adapt the site to the predominant type of user or, in some cases, to customise the display to the type of device detected.
Advertising: Those to do with third-party advertisers whose adverts appear on the site. These are not listed below as we don't have any direct control over them. For Google adverts you can change your preferences on Google's site.