Drift ice consists of sea ice that floats on the surface of the water in cold regions, as opposed to fast ice, which is attached ("fastened") to a shore. Usually drift ice is carried along by winds and sea currents, hence its name, "drift ice".
When the drift ice is driven together into a large single mass, it is called pack ice. Typically areas of pack ice are identified by high percentage of surface coverage by ice: e.g., 80-100%.
An ice floe is a large piece of drift ice that might range from tens-of-yards to several miles in diameter. Wider chunks of ice are called ice fields.
The two major ice packs are the Arctic Ice Pack and the Antarctic Ice Pack.