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.
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.