1. The Fed left rates at zero
At its just-ended Sept 16-17 policy meeting, the Federal Reserve decided to keep benchmark US interest rates at zero, citing weakness in the global economy and unsettled financial markets. It would have been the US central bank's first rate hike in nearly a decade.
A slump in equities over the past month, sparked by fears over the strength of China's economy, "may restrain economic activity", the Fed warned in its statement. This could put "downward pressure on inflation in the near term".
The delay was not a surprise as the majority of traders were betting that the Fed would hold fire for now.
2. Fed was more "dovish" than expected
A more "dovish" Fed is one that is less likely to raise interest rates, as opposed to being "hawkish".
While the Fed maintained its "bias" towards a rate hike sometime this year, the number of policymakers expecting no move in 2015 doubled and officials shaved back their projections for the pace of interest rate increases.
The Fed statement that accompanied the rate decision was also seen as "uber-dovish":
"People thought if they weren't going to raise rates this time, they would come out with a hawkish statement, and they didn't do that at all," said Thomas di Galoma, head of fixed-income rates and credit at ED&F Man Capital Markets in New York. "If anything, they came out with the contrary statement that was uber-dovish, that they were worried about the international situation."
3. Change in tone was driven by Fed's worries over China and emerging markets
Fed chief Janet Yellen told a news conference: "A lot of our focus has been on risks around China, but not just China, emerging markets more generally and how they may spill over to the United States.
"We've seen significant outflows of capital from those countries, pressures on their exchange rates and concerns about their performance going forward. The question is whether or not there might be a risk of a more abrupt slowdown than most analysts expect."
Ms Yellen, in contrast, was relatively bullish about the US economy, saying its strength had impressed Fed policymakers.
4. Markets now more confused about what matters most now to the Fed
Michael Feroli, US economist at JPMorgan, told the Financial Times: "I came away a little less certain about what are the criteria that are most important right now. It seems like the dollar in particular, as well as financial conditions and the globe, are more important than they seemed a few months ago, in terms of their prominence in Fed communications."
5. Wall Street banks now eyeing December for Fed rate liftoff
There are only two more meetings this year for Fed policymakers, in October and December. Economists said that based on the Fed announcement's language, they are ruling out October.
A majority of Wall Street's top banks now expect a December rate hike, according to a Reuters poll.
Twelve of the 17 primary dealers, or the banks that deal with the Fed directly, polled said they expect the Fed to raise rates in December. Two pegged the date at the Fed's next rate-setting meeting in October, and three in March 2016.