First and foremost they provide the ability to log in to the site. Without a cookie it is very hard to remember who you are from one page to the next, which makes posting messages on the site almost impossible. This cookie lasts for 30 days or until you log out.
The second use for a cookie (and probably the most important one) is to remember if you have clicked "Close this popup" on the cookie alert popup. Without that the popup would keep coming back, which would really annoy you. This cookie lasts for up to a year.
Yes. All browsers provide a means to remove cookies. For instancein Google Chrome you select the (i) symbol next to the URL at the top of the window.
There will be no consequences deleting the cookies for this site. All that will happen is that you will be asked to log in again and the cookie information popup will re-appear.
This is a report showing you the cookies set on your computer or device by this website.