Difference between static and relative positioning

Static positioning is the default positioning model for elements. They are displayed in the page where they rendered as part of normal HTML flow. Statically positioned elements don't obey left, top, right and bottom rules:

Relative positioning allows you to specify a specific offset (left, top etc) which is relative to the element's normal position in HTML flow. So if I have a textbox inside a div I could apply relative positioning on the textbox to have it display at specific place relative to where it would normally be placed within the div:

There is also absolute positioning - whereby you specify the exact location of the element relative to the entire document, or the next relatively positioned element further up the element tree:

And when a position: relative is applied to a parent element in the hierarchy:

Note how our absolutely-position element is bound by the relatively-positioned element.

And lastly there is fixed. Fixed positioning restricts an element to a specific position in the viewport, which stays in place during scroll:

You may also observe the behaviour that fixed-positioned elements do not cause scroll because they are not considered to be bound by the viewport:

Whereas absolutely-positioned elements are still bound by the viewport and will cause scrolling:

..unless of course your parent element uses overflow: ? to determine the behaviour of the scroll (if any).

With absolute positioning and fixed positioning, the elements are taken out of HTML flow.

In answer to "why CSS would still implement position: static;" in one scenerio, using position:relative for a parent and position:absolute for the child limits the scaling width of the child. In a horizontal menu system, where you could have 'columns' of links, using 'width:auto' does not work with relative parents. In this case, changing it to 'static' will allow the width to be variable dependent on the content within.

I spent a good few hours wondering why I couldn't get my container to adjust based on the amount of content within it. Hope this helps!

Position relative lets you use top/bottom/left/right for positioning. Static won't let you do this unless you use margin parameters. There's a difference between Top and margin-top.

You won't need to use static much as it's default

You can see a simple overview here: W3School

Also, if I recall correctly, when declaring an element relative, it will by default stay in the same place as it otherwise should, but you gain the ability to absolutely position elements inside it relatively to this element, which I've found very useful in the past.