When you visit some sites, it is common to get a privacy notification like this,
So what are these cookies?
While browsing some websites, the server gives you a cookie that acts as your identification card. Your browser stores that cookie file.
Upon each return visit to that site, your browser passes that cookie file back to the server. In this way a web server can gather information about your visit to the web pages and the information you have volunteered like login credentials, interests etc. So that you don't need to re-enter this information each time you visit the site.
Cookies play an important part in internet experience. Without cookies, you have to login again, open all the tabs or rebuild your shopping cart if you accidentally close the page.
Cookies can personalize your sessions by providing targeted ads that you might enjoy by knowing your interests. Ex: if you browse more cookery websites, it serves you ads on cooking.
Authentication is an another major advantage. Cookies can streamline login information, so users don't have to remember site passwords.
Cookies by themselves are not harmful, since they are directly created by the websites you are using. Sometimes cookies are created by the ads that are displaying on the website. They are called third-party cookies.
Third-party cookies are the one that creates risks and let advertisers track an individual's browsing history across the web on any sites that contain their ads.
Cookies are optional part of your internet experience. It is up to you to choose and limit what cookies end up on your computer or mobile device.