In any currency pair, the base currency is the first one listed and the quote currency is the second — the price tells you how many units of the quote currency it takes to buy one unit of the base. In GBP/JPY, GBP is the base and JPY is the quote, so the price shows how many yen one pound buys.
When you go long a pair you're buying the base currency and selling the quote currency; going short reverses that.
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Guide
How to Check the Way a Currency Is Managed
The regime behind a currency is published, not inferred. The four primary sources that say how a rate is governed, what each one can and cannot tell you, and how to keep the answer from going stale.