Majors vs crosses vs exotics
Forex Foundations
The dollar defines a major
Major pairs all include the US dollar on one side, like EUR/USD, GBP/USD, and USD/JPY. They carry the highest volume and the tightest spreads of any pairs in the market.
No dollar, still liquid
Cross pairs, like EUR/GBP or GBP/JPY, trade two major currencies against each other without the US dollar involved at all. They're liquid, just not quite as liquid as the true majors.
Wider spreads, thinner books
Exotic pairs combine a major currency with a currency from a smaller or emerging economy. They typically carry noticeably wider spreads and thinner liquidity than majors or crosses.