Merchandise or visible imports relate to physical goods. Imports of services are payments to foreigners for invisibles such as shipping, travel and tourism; financial services including insurance, banking, commodity trading and brokerage; and other items such as advertising, education, health, commissions and royalties.
In practice, many countries give prominence to visible trade figures because they are among the most reliable and rapidly available figures on external flows.
Even so, they are available only after a lag, are frequently revised as more information comes to hand and are subject to various errors and omissions.
Figures for invisibles are harder to collect, less reliable and are published only quarterly by some countries.