learned a lot~

Flag of Ukraine is Blue and Yellow horizontal strips.
Blue on top and Yellow on bottom.
Yellow mean wheat fields. Blue mean clean sky.

But very much for a long time flag the flag has been turned. Yellow on top and blue on bottom.
Yellow mean Sun shine and blue Dniper river.

Canadian flag is white with a red maple leaf, and two red bands on the edge. The maple leaf is a common tree, that changes colours due to the seasons. As for the bands, I'm not sure what they mean.

Turkish flag, moon and a star on red, they say it was the reflection of moon and star on blood of our people. But this symbol actually goes way back to ancient history - because its also an important mythological or astronomical symbol. And it has been used by Sumerians (the birth place of civilization)

The British 'Union Jack' Flag is very complicated.  It is the combination of three flags together.  The red cross on a white flag of England.  The St Andrews white cross on a blue flag of Scotland.  The red cross on a white flag of Northern Ireland.  When you put these three flags on top of each other it makes the British Union Flag :D