No one is 100% safe from having their website hacked (even the FBI's website is hacked). Here is a quick overview of what hacking is, how to fix hacks, and how to prevent future security breaches.
The "Front End" refers to everything that happens on a website's "client" side. Whatever is displayed in the browser, from the interface to the "effects" on the front end of a web application, has changed a lot over the years. And so has the work of those who do it!