Everything is done with HTTP requests (duh), if you want to upload a file then you make an HTTP POST request with the file data (just like with a normal file upload form) and the associated meta-data. The servers then process the file and give you links back to access it.

Fetching files will be processed similar to a download, php will "fetch" the file and then write it to disk. Then php can move or rename it via its functions.

Renaming, copying, and deleting files are all done with a single http request with a relevant response code (pass, fail, more info needed...).

Really, it's pretty simple and the included libraries seem to cover everything that most apps will need.

Check out the first couple bullet points on the "About the API" page:

> Simple HTTP+JSON method of accessing a user's information in a user approved sandbox on the user's desktop. List, upload, delete, move, copy, and get files as well as many other features... A full event callback API allowing you to get simple asynchronous events to your web site or service whenever the user changes their sandbox.