In the Web development world, what exactly do backend/server-side programmers do? I guess I don't really understand the whole concept.I've done the HTML/CSS layouts and website design and a little bit of SQL with PHP (still enhancing my skills, it's more of a side project for me).  I've also done a  small amount of JavaScript/JQuery.But I don't understand the backend work, such as the scripting languages (Rails/Python/etc) and such. What exactly do you do with them?
I don't really understand Backend/Serverside when it comes to web-development?
web development;web design
The basic premise is:The user gives his input, sends it over a network of some kind and the server then does it's magic according to the input.Basically you want all the security and validation to be performed server-side. With the niceties running client side, like unobtrusive form validation (you still need to validate server side though!). The big question: Why?Users can modify information on their machine. As an example see game trainers which modify memory values to let users 'hack' the game. If you do the core things on your machine, on your physical premises, you significantly lower the chances of someone tampering with your security checks. 