When there is a war or some other armed conflict in a country, many people will try to flee (run away) from that country. They will go to other countries, around the country where there is no war. Because they fled, they are called refugees.
If there are just a few refugees coming into a country it is generally no problem to get housing for them somewhere. However, if there are many (or if the government of a country expects many) refugees, it may build what is called a refugee camp. This is usually done by putting many tents, and a few toilets and showers on an unused plot (stretch) of land. This is usually land where no one wants to live.
Usually the governments hope that conflicts get resolved soon, and that those camps are only temporary.
This has not been the case for the refugee camps in the Gaza Strip, for example. Those camps have existed since the mid-1970s.