Is the visa for going abroad also to prevent prisoners?

The visa for going abroad is to prevent prisoners. Visa plays an important role in checking and controlling entry-exit personnel, protecting national security and preventing illegal immigrants and criminals.

Passport is the holder's nationality and identity certificate, and visa is the permission certificate of a sovereign country to allow foreign citizens or their own citizens to enter, exit or transit.

Visas are generally endorsed on passports, some are endorsed on other travel documents instead of passports, and some are issued separately. For example, immigration visas in the United States and Canada are A4 paper, and Singapore also issues separate paper visas to foreigners. Generally speaking, a visa must be used at the same time as a passport to be valid.