A glacier is a very large, natural piece of ice, which can move very slowly downhill, like a slow-motion river of ice. They are found in high mountain ranges and other places where ice never completely melts. In the distant past (many thousands of years ago) glaciers gradually flowed down and spread out over Europe and America, changing the shape of the land, during the ice-ages. One can still see glaciers today in places such as the Alps, the Himalayas, and Antarctica, although they are now melting due to climate change.
A glazier is a kind of craftsman who works with glass—one of two kinds; glazier can refer (1) to a person who puts glass into window frames, or (2) to a person who puts a thin glass-like coating on pottery (ceramics).