why div go bottom of page code example

Example 1: keep div at the bottom of page

#footer {
    position: fixed;
    bottom: 0;
    width: 100%;
}

Example 2: Make div bottom page

#container {
    position: relative;
}
#copyright {
    position: absolute;
    bottom: 0;
}
or 
#copyright {
    position: absolute;
    bottom: 2rem;
}