.box {
    margin:20px;
    width:300px;
    height:300px;
}

.posRel {
    background:crimson;
    left:50px;
    top:100px;
    position:relative;
    z-index:2;
}

.parent {
    margin:20px;
    width:400px;
    height:400px;
    background:salmon;
    z-index:10;
    position:relative;
}

.posAbs {
    background-color:blueviolet;
    width:100px;
    height:100px;
    position:absolute;
    top:20px;
}

.element {
    background-color:aliceblue;
    width:100px;
    height:100px;
}

.posFix {
    position:fixed;
    width:300px;
    height:300px;
    background-color:lightgreen;
    top:0;
    right:0;
}