From what I can gather, it effectively means that you get a 2GB virtual machine (other tiers allow custom memory sizing) that runs the IDE/analysis tools on top of it. Since you get 20 GBh/month, that means that you get 10 hours of usage free per month. If it was viable for my workflow, I would have to start by looking at the $19/month plan minimum, which would allow 50 hours of 4GB machine usage/month (or 100 hours of 2GB machine time). I doubt I would be a great analyst with a literal meter running, though, even if I was reasonably sure that I had enough time for a given month.