I assume he's referring to harvesting of resources in space - e.g. comets contain large amounts of (frozen) water, so one way of getting water into space could

I assume he's referring to harvesting of resources in space - e.g. comets contain large amounts of (frozen) water, so one way of getting water into space could be to send small spaceships up to harvest it from comets, rather than big spaceships full of water that is then costly to power up out of earth's gravity well. Of course, how you get that water to the target is another matter - getting it to a space station could be hard, but maybe you could pull chunks off the comet and send them crashing into, say, Mars. This might be a way of 'terraforming', to get water into the atmosphere, maybe even allow some of it to collect into small lakes, then you send some probes over with plants to start growing, bootstrap your way up.