Bart takes us on a time traveling adventure with Git. By using commands like `git diff` we can see changes over time, but we can actually see older versions of the code in a couple of ways. Using the `archive` command we learned out to pull just the files at a certain point in time (without the history) and the more terrifying `checkout` command that creates a "detached HEAD"! Bart even explains why that phrase was introduced and what it actually means. This was a fun lesson and a good foundation for what we'll learn next time, when we'll learn about stashing and branching to control the past and future.