USD/JPY tells you how many Japanese yen one US dollar is worth. It is one of the most heavily traded pairs in the world, with deep liquidity around the clock, and it sits at the centre of global interest-rate and risk flows.
The dominant driver is the policy gap between the Federal Reserve and the Bank of Japan. For years the Fed has held interest rates far above the BoJ's near-zero settings, which rewards holding dollars and has pushed USD/JPY higher. When that divergence widens, the pair tends to climb; when it narrows — the Fed cutting, or the BoJ tightening — it can fall quickly. Closely tied to this are US Treasury yields, especially the 10-year: rising US yields usually lift the dollar against the yen, and falling yields weigh on it.
Risk sentiment is the other half of the story. The yen is a classic safe haven, so when markets are nervous it tends to strengthen and USD/JPY drops. The pair is also the heart of the "carry trade" — borrowing cheaply in yen to buy higher-yielding assets — which lifts USD/JPY in calm times but can unwind violently when volatility spikes. Traders also watch for signs of intervention by Japanese authorities when moves become disorderly.
USD/JPY is liquid through all three major sessions: it moves on Japanese flows and data during Tokyo hours, sees fresh positioning in London, and reacts most to US data and Fed commentary during the New York session. Because so many forces pull on it at once, Robin's job is to weigh them together and turn the balance into one clear read — with an entry, a stop and a target.