If I buy logs and built rafts with them, which I then sell to people trying to cross a river, I'm creating wealth. If I own a strip of land up and down the river and charge people who want to cross it in their rafts, I'm extracting rents. If I patent the concept of raft building and require anyone building their own rafts to pay me, I'm extracting rents.

What that quotation means is that all the finance MBAs and Wall Street quants of the last decade aren't making the economic pie bigger, they're just ensuring that they get a bigger slice of it.