Resize Dinamically! Help!

Hi all! I saw this web site
and I would like, if anyone know, to learn how can I make that kind of resizing when I click on a section… the borders automatically resize to the position of the content. Is it made with php?
any tutorial about this?
sorry for my english if I have some mistake
please help! I wanna learn this, thanks!

Eugenia from Argentina :thumb: :nerd: