Basically you have four position states, which are as follows:
- static (default)
- relative
- fixed
- absolute
The difference between relative and absolute is that relative is "relative" to itself (left:15px will pad it to the left with 15px), but absolute is relative to its parent (first non-static parent that is) and applying the same attribute (left:15px) will result in it being shifted 15px away form the left edge of the parent element.
This is actually a fascinating study and will help immensely in understanding web layout.
