英国国旗图案代表什么意思啊？

国旗的意义在英文正文的2、3两段

“The Union Flag”, also known as the “Union Jack”, is the national flag of the“ United Kingdom of Great Britain and Northern Ireland”. Historically, the flag was used throughout the former British Empire. It retains an official or semi-official status in some Commonwealth Realms, e.g. in Canada, where it is known as the Royal Union Flag. The current design dates from the Union of Great Britain and Ireland in 1801.

SINCE 1801
The current Union Flag dates from 1 January 1801 with the Act of Union 1800, which merged the Kingdom of Ireland and the Kingdom of Great Britain to form the United Kingdom of Great Britain and Ireland. The new design added the red saltire cross of St Patrick's Flag for Ireland. This saltire is overlaid on the saltire of St Andrew, but still beneath the cross of St George. The Irish saltire is arranged counterchange with the saltire of St Andrew, so the white is always on the clockwise side of the red. The arrangeme