According to Wendy Chun, software stands as a metaphor for the invisible things that surround us every day, the things that we don't fully understand but that we have come to rely on to produce visible effects that we now take for granted. With that background in mind, let's break down this quotation.
Software, Chun says, is defined by its separation from hardware. It makes us think that we know what we are seeing, that we understand what we are looking at when really we do not. This is quite true. Think about the word processing software you use frequently. Do you really understand how it works? You probably just take for granted that it does work, that letters will appear on the screen as you type and that you can save your documents and access them as you need them again.
As such, software is a sign that points to other things in our culture (this is the meaning of indexicality). We don't often understand the complex processes going on in the world around us. We see people's actions, for instance, but we don't always (or usually) grasp the ideology that drives them. Yet software, with all its mysteries, reminds us that what we see in execution or process or action is always backed up by some sort of “program” or “order.” These naturally go together, even if we pay little attention to them.
Chun goes on to remark that programming languages are part of this invisibility behind the visible. They have their own characteristics and their own methods of control and discipline (which Chun claims is gendered). Software both conceals and reveals. It conceals processes and reveals results, but people need to be mindful that both are operative in software and in life.