<p>The Nikkei 225, also known as the Nikkei, is Japan's primary stock market index. It tracks the performance of 225 of the largest and most liquid stocks listed on the Tokyo Stock Exchange.</p>
<p><strong>Why it matters:</strong> The Nikkei 225 is a key indicator of the overall health of the Japanese economy and global investor sentiment towards it. It's often used as a benchmark for Japanese equities and can influence trading decisions in other Asian markets. For instance, a significant drop in the Nikkei can signal a potential slowdown in the Japanese economy, impacting global markets.</p>