About 8,000 migrants reached Germany aboard trains last weekend (see video below) after difficult, exhausting journeys through Hungary and Austria by bus and foot. Earlier, many crossed the Mediterranean Sea to Greece and Italy on jammed boats. They flee war and chaos in Syria, Afghanistan and elsewhere in the Middle East. In all, hundreds of thousands of men, women and children are making one of the largest emigrations since World War II, trying to reach peace, stability and economic security.

The human drama is a crisis that raises tough policy questions for European governments: How many migrants will be accepted and for how long? Does Germany’s open door for Syrians encourage more people to try treacherous, costly journeys from refugee camps in Jordan, Lebanon and Turkey? (Some have drowned as boats capsize.) Will other countries follow the lead of France and Germany, which propose that the 28 European Union countries each agree to take a specified quota of immigrants on the move?

The words "migrant" and "refugee" have a crucial legal difference. A refugee is someone who fled war or persecution, and can prove it. They're entitled to basic protections under international agreements, and can apply in Europe for political asylum or another protected status – at least temporarily. Refugees can't be sent back to countries where they'd be in danger. Migrants, by contrast, may be fleeing poverty, seeking better jobs or joining relatives who came earlier. Countries can deport migrants who arrive without legal papers.

Where are they from? Nearly half of the roughly 320,000 migrants reaching Europe in 2015 are from Syria. About 12 percent are from Afghanistan, 8 percent are from Eritrea in Africa and 3 percent are from Iraq. – United Nations

British leader says: "You've got a swarm of people crossing the Mediterranean, seeking a better life, wanting to come to Britain because Britain has got jobs." -- Prime Minister David Cameron

UN agency says: "One of the most fundamental principles laid down in international law is that refugees should not be expelled or returned to situations where their life and freedom would be under threat." – UN High Commissioner for Refugees, Sept. 3, 2015