Barsel: Many websites need cookies to function. For example, if you're ordering several different items on Amazon, their servers need to know that it's the same person who just ordered gardening gloves who's also now ordering Lego, otherwise they couldn't keep track of your order and you'd have to sign in to every single page separately an pay for every item individually too.
So, in general, cookies are extremely useful and you most definitely need to have them enabled.
However there has been a lot of concern about a 'tracking cookies', which aren't just used on a single website but are shared between thousands of websites. They're the reason that, say, you search for pressure cookers on Amazon and then you'll see ads for pressure cookers suddenly appearing on AB and elsewhere. (Or, if say, you post on a thread about garden sheds on AB, you'll find other websites showing you ads for garden sheds). Google have announced their intention to make tracking cookies (but definitely not ordinary cookies) a thing of the past:
https://www.wired.co.uk/article/google-chrome-cookies-third-party-ads