This is the first step in developing the techniques required to sustain life in space without having to haul everything up Earth's gravity well. If we can get good at this, then it changes the entire economics of space.
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.
I am guessing OP is referring to the ability to reliably orbit and land on comets (and asteroids). We can use them for manned way stations or construction platforms. Not to mention mining them for whatever useful stuff may be in there.
If we could show that comets have available surface water ice in the right form, then their gravity is low enough that you could plan to drill it off and melt it to be fed into water-ion thrusters. That would let you at the very least launch a mission which could study one comet, refuel, then slingshot away to a different target.
