Understanding User Engagement and Retention

It's "Marketplaces Week" for us at a16z, thanks to our consumer team releasing a new index of the next industry-defining marketplaces, the Marketplace 100.  

But what happens as such marketplaces and other platforms evolve over time, as do their users? This episode is a rerun of a popular conversation from a couple years ago -- featuring general partners Andrew Chen and Jeff Jordan (in conversation with Sonal Chokshi) -- on what comes after user acquisition: retention. 

It's all about engagement. So what are the key metrics? And if different kinds of users join a  platform over time -- what does that mean for engagement, and where do cohort analyses come in?