You see the website in the browser such as Google Chrome, Internet Explorer or Microsoft Edge, Safari, or Firefox. There is a bunch of others but I will be using Google Chrome for the explanation. Others have the same features, even magic F12 button works for all of them the same. Browser works as a showcase, straight in front of your eyes. Developers call it front-end.
To see the page the user enter page address in address bar of the browser. The browser requests the code of that page, and server answers that call, generating the front-end code, suitable for the browser to decode. We cannot see what is there, it is back-end.
Sometimes you need specific information and you fill the form on the page to ask the question. The place with such data is Database.
This structure should exist somewhere to be accessible for the public, e.t. be hosted somewhere.
Now you know the four main terms. They are front-end, back-end, database, and hosting.