The lecture focuses development track and provides a look into Ethereum consensus layer client codebase, explaining its architecture and functions.
Paul dives into Teku, consensus client implementation in Java and explains an example on how an EIP gets implemented. You should have at least basic knowledge of the language syntax to follow properly.
Consensus-specs is executable, and a passing knowledge of python may be beneficial, but it's a fairly easy language to reason about at the level the specs are written.
Additionally, you can get ready by studying the following resources: