A droplet is a regular application containing a “on open” handler (which will enable your app to receive drag & drop items in the Finder). Eg:
on open aliasListOfFiles
repeat with i in aliasListOfFiles
display dialog (i as text)
end repeat
end open
Save as app, and you are done. Now, you can drop items onto your app’s icon, and the “open” handler will be invoked, receiving as parameter a list of aliases.