Why when I somtimes download an application online it sometimes stores application and all files in download file and not in application folder?

is it ok to just move applcstion folder tmfrom download folder to application folder and leave all the other text documents and other folders in download folder?

is it ok to move application file to application folder and leave other files in download folder?

The download folder is a feature in Leopard to let you keep track of what you’ve downloaded. Once you install the app it should be in your Applications folder, hower some apps don’t come with an installer, just drag and drop in to desired location.
You may want to check what’s selected as destination when running the installer to make sure it goes to the Applications folder.

so if I can click the application icon and application starts running. Can pretty much assume the application is installed correctly. So is it safe and do I always have to do manualy delete all the files in my download folder? I mean after awhile that free gets big

If its a self contained application, ie doesn’t come as a file called something installer, you can just move it from one folder to another. With regards to deleting what’s in your downloads folder, just make sure its also in another location if you don’t want to loose it