Day 1 - frontend When you visit a website, there is some code that runs on a different computer elsewhere & some code that runs on your browser/computer. The part of code that runs on your browser/computer constitutes what we call "Frontend".
Day 2 - request/response Whenever we open any url in the browser, the browser has to ask an appropriate computer for the content at that particular url. It does so by sending a "request"... literally making a request. The content it gets back from the "request" is a "response"
Day 3 - cookies Cookies are small pieces of data you can store in the browser. They are website specific i.e. can't be accessed on another website. Cookies of a particular website also go along in all the requests sent to that website urls.