Major pairs all include the US dollar. The seven classic majors: EUR/USD, GBP/USD, USD/JPY, USD/CHF, AUD/USD, USD/CAD, NZD/USD.
They concentrate ~75% of global volume. Their spreads are the tightest, their liquidity the deepest, their behaviour the most studied. They are the gateway.
EUR/USD alone accounts for ~24% of forex volume. If you are starting out, it is the instrument to know inside out before any other.