position absolute + position fixed code example

Example: absolute css

/*hey guys if you have doubt how absolute property works, it works in way that 
it  comes out of the 'document flow' i.e) just consider two div elements in
which each a size of a box, say that you need two place the second box over the 
top box simple just give it absolute position such that the second div 
positioned itself with respect to the browser window, you can move the element 
anywhere in the window*/
div{
  position:absolute;
  top:10px; /*it pushes away div element from top 10px down Remember with
  browser window*/
  left:20px;
  right:10px;
  bottom:20px; 
  /*last three property excatly similar to top property it just pushes away 
  from specified direction*/
}
Wondering how to use absolute property within a div simple?
Say you have a div inside a div. /*most case scenario*/
putting first div relative and mentioning second div absolute will do the job
In my early days of css, I wonder the position property with relative and no top
bottom, right left property with it. One day I realized it.
/*highly recommed you to run the following code two know the difference*/
1st)<div class='b'>
        <div class="b1">
            content
        </div>
 </div>
<style>
.b {
    height: 200px;
    width: 200px;
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: rgb(201, 14, 14);
    position: relative;
}

.b1 {
    height: 100px;
    height: 100px;
    width: 100px;
    position: absolute;
    top: 50%;
    left: 50%;
}
/*do it and see*/
2nd)<div class="b1">
content
</div>
<style>
.b1 {
    height: 100px;
    height: 100px;
    width: 100px;
    position: absolute;
    top: 50%;
    left: 50%;
}
1st with reference to the first div
2nd to refrence to the object window
Wondering Why i use div for all my tags, simple due its flexibilty to be an
comman container
</style>
    ---By Siddharth -a physics undergraduate.