16 January 2016 Last updated at 09:12 GMT
Many travel great distances in search of a better life in Europe and some end up living in a makeshift camp in Calais in France hoping to make their way to the UK.
Now the French government have asked them to leave parts of the camp that are close to a motorway.
Watch this report from BBC Reporter Simon Jones.

Kenya's government said Mohamed Kuno was behind the attack in April 2015 that killed 148 people.
Regional forces in Somalia said he was one of 16 people killed in an overnight raid on their convoy in Kismayo, a port city in southern Somalia.
Four of those who died were reportedly senior members of the al-Shabab Islamist militant group.
The BBC's Africa security correspondent, Tomi Oladipo, said the news comes as a huge boost for Somalia and its allies in the fight against al-Shabab.
However, at least 10 people were killed on Wednesday by a car bomb outside a hotel in Somalia's capital Mogadishu, that was claimed by al-Shabab.
The news of Kuno's death was confirmed in a press conference held by Abdirashid Janan, the security minister in the Somali region of Jubaland.
Mohamed Kuno: Kenya's most wanted
Africa Live: Latest updates
After the Garissa attack, Kenya's government put up a $215,000 (Â£149,000) reward for Kuno's capture.
A Kenyan-Somali, he was a headmaster at a madrassa, or Islamic school, in Garissa until 2007.
But then he crossed the border into Somalia to join the Union of Islamic Courts (UIC), which at one point controlled much of the country.
When the UIC collapsed, he joined the militant group Hizbul Islam, which in 2010 merged with al-Shabab.
He had several aliases but was best known as Mohamed Dulyadin, which means ambidextrous in the Somali language. He was thought to be in mid-30s.
Attack as it happened
Who were Garissa victims?
Why does al-Shabab target Kenya?
In the university attack on 2 April last year, four al-Shabab militants shot students in their dormitories before rounding up and killing dozens more.
The four gunmen were killed during the siege but it took 16 hours for anti-terrorism forces to bring the attack to an end.
It was the deadliest attack in Kenya since al-Qaeda's bombing of the US embassy in Nairobi in 1998, which killed 213 people.
It also came a year and half after al-Shabab fighters targeted the Westgate Mall in Nairobi, killing 67 people.
Kuno is alleged to have been behind several attacks on Kenyan soldiers who are fighting al-Shabab in Jubaland. He was also blamed for attacks on Kenyan civilians in Kenya itself.
Al-Shabab says it is retaliating for acts by Kenya's security forces, which are part of the African Union's mission in Somalia against the group.
1. Militants enter the university grounds, two guards are shot dead
2. Shooting begins within the campus
3. Students attacked in their classrooms while preparing for exams
4. Gunmen believed isolated in the female dormitories
5. Some students make an escape through the fence
Migrants and refugees have been leaving their homes in places like Syria and Afghanistan, where there is fighting, in big numbers over the last year.
[NEXT_CONCEPT]
The leader of the attack on Garissa University in Kenya has been killed, officials in Somalia say.