LIGO and Virgo have observed over 40 mergers of black holes, including black holes in neutron star- black hole systems. I will describe the properties of the binary black hole population, including the mass distribution, the spin distribution, and evolution with redshift. The population distributions encode astrophysical lessons about how, where and when black holes are made. I will discuss some of these lessons, including understanding the pair-instability mass gap in light of massive black hole observations, and inferring the time delays that black holes experience between formation and merger. Several mysteries remain about the origins of these black holes, and I will discuss what we expect to learn from future observations.
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