It means that you can write pure functions (in the functional programming sense) where one (or more) of the arguments to your function is a _database value_. In

It means that you can write pure functions (in the functional programming sense) where one (or more) of the arguments to your function is a _database value_. In haskell the types to a query function would perhaps look like this: query :: Query -> DBValue -> Result instead of performQuery :: Query -> IO DBConn -> IO Result