An ensign is a special flag that represents a country or a ship. It's like the flag that you see outside your school or your house, but it's bigger and it has its own important meaning.
When a country has its own ensign, it usually has specific colors and designs that are unique to that country. For example, the United States has a flag with red and white stripes and a blue rectangle with white stars.
On a ship, an ensign is really important because it tells people which country the ship belongs to. It's like a way of saying "This ship is from the United States" or "This ship is from England." When a ship is sailing, the ensign is usually displayed on a special flagpole at the back of the ship, so that other ships and people can see it.
Overall, an ensign is a very special kind of flag that represents something really important, like a country or a ship. It often has special colors and designs that are unique to that ensign.