Explain the difference b/w arr.length and arr[row].length

#1

package Arrays2D;

public class Basics {

public static void main(String[] args) {
	// TODO Auto-generated method stub
	
	int row=4;
	int col=2;
	int[][] arr=new int[row][col];
	System.out.println(arr.length);
	System.out.println(arr[row].length);
}

}

//Last Syso showing error; please explain it briefly

#2

arr.length gives the number of rows in a 2-d array
arr[row].length gives the number of elements in that row
if the array is uniform , arr[row].length is equal to the number of columns
In java arr[][] is actually a array of arrays, hence arr.length gives number of arrays and arr[row].length gives number of elements in that row array