Paint in Windows 11 format?

Hello

1.
When opening Paint in Windows 10, you see a white blank canvas.
What is that format?
Is that just Paints own format / data in memory?

2.
If I draw something in Paint in Windows 10- window 1
Open another Paint window – window 2
If I copy the picture in Paint from window 1 to window 2, then what is the format in the copy holder? bitmap? Paints own format / data?

Thank you