A currency has no price on its own, only a price in another currency. So every Forex trade is two trades at once: buying one currency and selling another.
Buy EUR/USD and you are buying euros and selling dollars at the same time.
The first currency in a pair is the base; the second is the quote. The price is how many units of the quote currency buy one unit of the base.
Buying EUR/USD expresses the same view as selling USD/EUR: you expect the euro to strengthen against the dollar. The inverse price is simply 1 divided by the original.
Majors pair the US dollar with another large, stable economy: EUR/USD, USD/JPY, GBP/USD, USD/CHF, AUD/USD, USD/CAD and NZD/USD.
They make up most of daily Forex volume, so they have the tightest spreads and the deepest liquidity.
Minors, also called crosses, pair two major currencies without the US dollar, such as EUR/GBP, EUR/JPY or GBP/JPY.
They are still liquid, but spreads are usually a little wider than on the majors.
Exotics pair a major currency with one from an emerging or smaller economy, such as USD/TRY or EUR/ZAR. They can move sharply on local politics, and spreads are typically many times wider than on the majors.
Liquidity falls and cost rises as you move down the list.
