签证上的ON表示什么？
Visa stamp on a passport is the most important document for travel abroad. There are many different visas and visa types， but there will be two main parts of it： Visa Stamp & Visa Expiry Date.
1) VISA STAMP is where they put their name， photo and stamp in your passport and state validity date when you can travel to that country or region within 90 days (sometimes less). It's also called “visa sticker” as it used to be printed/sticked into your passport before digital scanning was applied by embassy， consulate etc. In this way， each country has its own design for stamps according to national flag colour(s)， letter size（usually A4）and layout. The format may change from time to time due to new technologies so do pay attention to them if needed.
2) VALIDITY DATE is often located beside visa stamp， which shows how long you have to stay in the destination country after entering that country. If not specified explicitly， usually valid stays are calculated based on "from the day of entry" instead of "from the day of issuance"， except some special cases such as multiple-entry visas with unlimited stay between visits. Most countries require tourist and business visa holder to leave the jurisdiction at least once during period of validity， otherwise they should register themselves in advance with local authorities when applying extensions online via eVisa system等.
In addition， depending on type of visa issued， holders might need further requirements upon arrival including pre-arranged flights booking ticket proof， return travel plan etc. Some high risk travellers who are already blacklisted internationally would even meet more strict scrutiny while passing immigration control and might end up denied boarding to certain destinations altogether！ Therefore， always consider all the possible risks involved whenever choosing any overseas trips especially non-EU ones nowadays under current security situation around globe！ As such； don’t just stick only to cheap flight tickets offers because those could lead directly back