The ease with which a person can travel to another country depends on their passport.
Some countries are more forthcoming in letting visitors in than others.
For instance, anyone with a passport can visit Cambodia, which offers visas or visas on arrival to all.
Travelling to Turkmenistan, on the other hand, will prove to be quite difficult for most. All passport holders need to apply for a visa before making a trip.
The Passport Index explores how welcoming each nation is, based on the number of countries they accept visa-free or with a visa on arrival.
Below is a map showing which countries are least and most welcoming of foreign visitors.