The Fed's decision Wednesday to keep overnight rates unchanged initially seemed bullish, but stocks sold off after Chair Kevin Warsh's press conference before rebounding. Long-term Treasury yields hit a 19-year high following Warsh's Q&A, extending what bond watchers call a "bear steepener."

Despite the ominous name, a bear steepener isn't necessarily bad for stocks. It occurs when the Treasury yield curve's slope is positive and increasing. Steepening is welcome when driven by rising growth expectations, as seen in 2003, 2009, and 2021 during economic recoveries.

Microsoft shares rose while Apple declined amid the volatility. The market's reaction highlights the complex relationship between interest rates and equity valuations, with investors parsing whether higher long-term yields signal stronger growth or tighter financial conditions.