What is meaning of y = x++ <= 2 in C?

I have following code snippet in C Language.

int main()
{
    int x = 1, y = 1;
    for( ; y ; printf("%d %d  ", x, y))
    {
        y = x++ <= 2;
    }
    printf("\n");
    return 0;
}

It gives output like

2  1
3  1
4  0

I do not understand output and meaning of y = x++ <= 2.