JPanel said to be opaque what does that mean?

Question

In Swing JPanel said to be opaque, what does that mean?

Also how JPanel VS JComponent compared in relation to opaque?

Please explain if possible in simple te

Answer 1

Another useful reference is the section on Opacity in the article Painting in AWT and Swing. It's also helpful to know that JPanel is opaque by default on many L&Fs, while JLabel is not.