Your vote on this answer has already been received
A lake any body of water surrounded by land and very large lakes are sometimes called seas. The world's largest lake is the salty Caspian Sea at 143,200 square miles (370,886 Sq.km). The Caspian Sea is surrounded by Russia, Azerbaijan, Iran, Turkmenistan, and Kazakhstan.
The world's second largest lake, and the world's largest freshwater lake is North America's Lake Superior at 31,700 Sq.Miles (82,103 Sq.km).