This page gives an overview of the "project" concept as it relates to Aptana Studio and Eclipse.
Introduction
Both Aptana Studio and Eclipse use the idea of a "project"--a related group of files that are virtually grouped together in the Project View or Navigator View (depending on which IDE or plug-in you are using). In Aptana, you also have the option of working with files directly through the file system via the File View. All projects have their own folders and own ".project" file.
The benefit of working with a project is that you can create a project via a project wizard, which sets up all of the necessary files for your development work. For example, if you would like to create a web application and code against the Yahoo UI library, you can create a "Yahoo UI project" via a wizard, which sets up all of the JavaScript library files and Code Assist automatically for you.