A cookie a file your web browser creates, at the request of a website, that is stored on your computer. These files store information, such as shopping cart contents or authentication data.
A cache stores data from the website, such as text or images, so that the web page will load faster if you access them again.
Even if they are relatively small in size, they will accumulate over time. It could cause performance issues on your browser.
We highly recommend you clear out the cache and cookies once in a while to make your browser work better.