This Object return all the information related to the browser screen . Like width of a screen , height of a screen , color Depth and pixel depth etc .
Syntax :

window.screen

Some important property of screen :
1) width : It return the width of a browser screen .
2) height : It return the height of a browser screen .
3) availWidth : It return the available width of a browser screen .
4) availHeight : It return the available height of a browser screen .
5) colorDepth : It return the color depth of a browser screen .
6) pixelDepth : It return the pixel depth of a browser screen .
Example :
Script code :

document.write ( screen.width ) ; // Output : ex. 1366 , it return value based on your browser
document.write ( screen.height ) ; Output : ex. 768 , it return value based on your browser
document.write ( screen.availWidth ) ; Output : ex. 1366 , it return value based on your browser
document.write ( screen.availHeight ) ; Output : ex. 728 , it return value based on your browser
document.write ( screen.colorDepth ) ; Output : ex. 24 , it return value based on your browser
document.write ( screen.pixelDepth ) ; Output : ex. 24 , it return value based on your browser