Yield relates to the return on capital invested in a bond. When prices rise due to increased demand, yields fall and vice versa. The yield curve is a graph with the daily yields of U.S. Treasury securities plotted by maturity.
An inverted yield curve occurs when the interest rates (yields, to be more specific) on short-term bonds are higher than the interest rates on long-term bonds. The specific trigger compares the 10 year treasury to the 2 year treasury.
On December 14, the Federal Open Market Committee (FOMC) voted unanimously to raise the federal funds rate by 0.25% — to a range of 0.50% to 0.75%. This was the second increase since December 2008, when the benchmark rate was lowered to a near-zero level (0% to 0.25%) during the Great Recession.