For most people it probably means using fewer plastic bags or turning the thermostat down a couple of notches. Maybe you marvel at what wind turbines or solar panels can do.
Yes, of course, there are these things but sustainability is a far wider issue than these. The Oxford English Dictionary defines it like this:
In essence it means everyone using a little less of what has always been used whilst maintaining the required increases in output.
Contemporary sources break sustainability down in to these four essentials: