Application Pages Vs Site Pages
Remember the difference between them in SharePoint (MOSS 2007)
Yesterday, somebody asked me the difference between the application page and site page in Sharepoint. Having developed five custom site and application pages in Sharepoint, I couldn't explain what exactly it is. I really got confused over time, as usual my brain was blank.
In a second after opening a SharePoint VS solution file, I got it. Just remember as the name indicates, Application pages can be used across SharePoint Web Applications and the Site pages are used across the Site(s). When you remember this, then you wont get confused. If its across applications then its the only _layout folder which is helping us. Wherein the site pages are the ones what we want to be specific for a site or to its contents and OOB example are AllItems.aspx, default.aspx etc.
Yes, I agree that working in a dozen of pages will also help you to remember, but in the beginning, even after a year, lot of things in SharePoint is confusing and time consuming. Main reason behind this is our lack of basic understanding and poor memory. I strongly recommend every SharePoint developer to read the Inside Microsoft Windows SharePoint Services 3.0 and a SharePoint administrator to read Microsoft SharePoint Services Administrator's Pocket Consultant.