A glaciation is a period of geological time when the climate gets cold and temperature is low. The result of that is formation of glaciers or ice sheets on land in polar, subpolar and temperate areas. Glaciations are also called glacial periods or ice ages.
Earth has experienced many glaciations the past 2,6 million years. When a glaciation finishes the climate gets warmer and earth is in a climate period called interglaciation.
The last ice age, which often in Europe is called the Weischelian, was coldest about 22.000 years ago and it ended about 11.700 years ago.