What is a productized service?

You may have heard some folks in the boostrapping and startup community use the term "productized service." You might be wondering: what is that?

For example, Bench is a bookkeeping company, but look at how they price and deliver their service:

You sign up for Bench the same way you would for a web app. You pay a monthly subscription. You get a dashboard. What's different, is behind the scenes, the service is performed by human beings.