For example if I apply this update - do this mean that it is not needed to apply any other update for IE8 with date earlier than 8/8/2011?
Yes, this is exactly what cumulative means, that it includes all prior updates.
For example Windows NT updates were cumulative (meaning you could simply apply the latest service pack available) but I do not believe that Window Vista or 7 service packs are cumulative and so you have to install the previous service pack before installing the next. At least that is how Windows updates gets the updates for you, SP1 gets installed before SP2.
As I have been corrected in the comments Windows service packs are cumulative hence you can simply install the latest service pack without the need to install previous service packs. I was simply not sure if they were due to the behavior of Windows Update that I have seen.