You only get it for 35 minutes. After that it's gone, or you can pay to keep it up.
When would I use this?
Among other reasons, perhaps:
*You need another computer to test something quickly.
*You need to install and use a utility for one thing, and don’t want to clutter your own environment.
*You need a vanilla environment to get something to build and run properly.
*You need linux but accidentally used windows.
Why shouldn’t I just spin up an ec2/rackspace/linode instance?
*They all make it slower and more difficult than it should be.
Get an Instant Server