I highly recommend this starred answer to that question by u/sowser.

As an addendum to that answer, I would add that Russia (or more technically Muscovy) had legal slavery (known as kholopy) until 1723, and this was a distinct group from serfs. The condition of and limitations on Muscovite slaves would be comparable to that of chattel slaves, but it was different in scale: kholopy were more like personal household slaves rather than a large, widespread agricultural workforce.