Special revelation is the direct communication from God. It is different from general revelation which is more about clues that God has left in the actions he has taken e.g. creation. We learn something about God by observing God’s actions but sometimes God speaks directly. An example of this kind of thing might be prophecy. Of course the best example is the special revelation of Jesus where God becomes incarnate and lives as and among us, you can’t get more special than that.
So what about the bible, is that special revelation? This is where things get complicated. I believe in some sense it is special revelation in that it is inspired by God to be a communication from God. However, the bible is not dictated (at least that is what the vast majority of Christians believe) so most of it is not a special revelation in the sense of a direct communication from God. Much of the bible, indeed, seems to be general revelation in that it points out where and how God has been at work rather than being a direct communication of God’s words.
Hope this makes sense.