"Up" refers to price in this case, specifically the price of Mortgage Backed Securities (MBS), which are the securities that directly govern mortgage rates. And "up" in price means "down" in rate.
We have 30 minutes to go until important economic data is released regarding economic indicators and the manufacturing sector, but earlier this morning, the Jobless claims report was released slightly worse than expectations. This is generally good for mortgage rates as a weak economy causes investors to buy more of those MBS we were talking about. That increased competition among buyers continues to drive prices up and thus rates come down.
After paring overnight gains in futures trading, the Dow still opened in positive territory, albeit only slightly. We will need the remaining economic reports to be weak in order to hold on to the great rates that should be coming down the pipeline in a few hours. Nonetheless, with strength in rates yesterday, unless there is a major stock rally today, we should still be in historically low ranges on most major mortgage types with wholesale rates (which don't account for closing costs, or lender profit) just below the mid 5's on a 30 year fixed.