There is a cookie that is used by Google in the ads shown on the publicity sites that show ads from AdSense for content (which expowera does). When a user visits an AdSense publisher's website and either views or clicks on an ad, a cookie can be placed in this end user's browser. The information that these cookies collect is used to help AdSense publishers better view and manage ads on their websites and the web.
In general, if you do not accept cookies, you will set your browser to automatically deny to receive cookies. You can also set the browser to tell that a webpage contains cookies.
Cookies are small text-based data files. They are saved in your computer (if you have permission for this - which you should do) and in most cases it may be useful when it comes to apply to your surfing. Cookies are many times available to give you access to various features and services available on a site. Read more at aboutcookies.org.
You usually talk about two types of cookies - Cookies and Session cookies.
Cookies: Used to maintain statistics, save usernames and passwords, facilitate login to various services, tell us what has happened to the site since the last visit, etc. How long such a cookie is stored in your computer is determined by the website.
Session cookies: Used during the time you are active on a site. They are only saved temporarily and disappear when you turn off your browser. For example, they will keep track of settings you make during your visit (such as language, text size, username and password).