What are glaciers?

http://www.google.com/webhp?sourceid=chrome-instant&rlz=1C5CHFA_enUS705US707&ion=1&espv=2&ie=UTF-8#q=glaciers

and

http://www.google.com/search?q=glaciers&rlz=1C5CHFA_enUS705US707&espv=2&biw=1437&bih=720&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjLis3_h4PRAhVnrVQKHeITAXMQ_AUIBigB