This is my first experience building web applications.
I read the agile guide in this site, but I have some doubts about it, and I hope that someone could help me to solve it.
I can't stand how it's possible to build an application avoiding the designing of it, avoiding the requirement gathering and ignoring all the problems that you could meet in the future as the interaction between modules.
For example how it's possible to design a database without seeing the entire design project ?!?

I know that for someone it could be a silly question, but I really don't understand some principles behind the agile method.