They are also used for other normal business activities such as tracking performance of ads for Bounce Metronome in Google search results or youtube, facebook etc, and to credit affiliates for any sales they generate for Bounce Metronome.
Introduction to cookies
In case you don't know what they are, cookies are small files generated by your browser that remain on your computer. The cookies themselves never leave your computer. However they can be used to transform the web pages that are presented to you, and the links you click on in the web pages.
Cookies are used to make things persist e.g. contents of your shopping basket
They ensure that items on the web site can persist for you - for instance that if you add something to a shopping cart, then return to the site later you will find that it is still in your cart - this is the way such things are normally done.
They also preserve your preferences for the site, For instance, there is a special version of each page on the Bounce Metronome website optimised for blind visitors (accessed through a link that's only visible to screen readers). If you choose to view this version of any of the pages on the site, your preference is remembered throughout the website. This is achieved by use of a cookie.
Analytics tracking to improve the content of the website
Analytics tracking for ads for Bounce Metronome
Cookies may also be used in a similar way to track the performance of ads I show for Bounce Metronome on Google search results etc.
Affiliate tracking to allow affiliates to be credited for sales
The usual way this is done is that the cookie is used to create a special url when you go to buy the product, for instance, it might append the affiliate id to the url. This makes it possible to pay the affiliate an agreed fraction of the price of the product for every sale that results from their referral, in a fully automated system.
Actually I don't have any affiliate system in place yet for Bounce Metronome but may do so in the future.
It's easy to opt out of google analytics tracking, get the Google Analytics Opt Out plugin
For the other cookies, you need to adjust the settings in your web browser, as cookies are set by the browser
What you can do depends on the browser. You may have options to disable some cookies and leave the ones that are essential for reasonable web browsing experience.
Warning - if you disable all cookies, then you might find you have to continually re-enter login details on every page of a website. You might also lose all the items from your shopping basket before you can complete your purchase, and encounter many other inconveniences.
In Chrome type this url into your address bar (it won't let you go to it just by clicking on the link) chrome://settings/content
In IE, see the instructions here: Block or Allow Cookies
In Firefox, see the instructions here: Enable or disable cookies in Firefox
For Opera, see these Cookie Tips
How this relates to the new EU law on cookies.
As a website for a business in the EU, I am required to follow the EU directive on cookies.