What is 'git reflog' and how does it differ from 'git log'?

git reflog (reference log) is a local tracking mechanism that records every update made to local branch pointers and the HEAD pointer. Unlike git log (which only shows the commit graph of the active branch), git reflog tracks commits, resets, checkouts, rebases, and merges. It acts as an undo history log for your local repository, allowing you to recover lost commits and branches.