Charge transport by holes is an important concept in semiconductor physics. In particular, it is important to understand charge transport by holes as different and separate from charge transport by electrons.
What makes this a tricky concept is that holes are generally described as the absence of an electron or slightly less informally as unoccupied electron energy states. In this view, holes are simply a convenient short-hand: when we talk of holes moving, it is simply an indirect description of an electron moving in the opposite direction.
So are holes real?
This is a much more subtle question than it may initially appear.
First of all, while it may seem lawyerly, at some level you do need to encounter the philosophical question of what it means for something to be “real”. See e.g. here, here and here.
As engineers, we would prefer to avoid such intractable questions. One possible approach is to avoid the question entirely: holes are a useful construct and that’s all that matters. An alternative, pragmatic approach is to treat holes as real to the extent we are able to observe and manipulate them in the same way that we observe and manipulate, say, electrons, which we know to be real (how?).
And this is where things get interesting: it turns out that you can observe holes in a very direct and satisfying manner using an elegant but simple experiment:
Some additional discussions of this question are here and here.
hawkee 