There's a considerable lack of documentation around exactly what it is you are getting. The pricing page has no info, the blog post has just a tiny bit more.

Heroku does a great job of really detailing their infrastructure and having that map to a dyno. PHPFog uses a different approach and details specs. Both are more transparent.

I assume a worker is a single thread (much like a dyno), but "Improve the reliability and responsiveness of your website." isn't nearly enough detail.