What is the fundamental difference in how `HEAD` (a symbolic reference) and a tag (a direct reference) point to commits?

The fundamental difference in how `HEAD` and a tag point to commits lies in their nature as references: `HEAD` is a dynamic, symbolic reference, whereas a tag is a static, direct reference.

`HEAD` is a symbolic reference, meaning it does not directly contain a commit's SHA-1 hash. Instead, `HEAD` typically points to a branch name, such as `refs/heads/main`. This indirection means that `HEAD` automatically tracks the latest commit on the currently checked-out branch. When new commits are added to that branch, the branch reference itself is updated to point to the new tip of the branch. Consequently, `HEAD` implicitly "moves" to represent this new latest commit because its target (the branch) has moved. `HEAD` represents your current working location and the parent commit for any new work.

A tag, in contrast, is a direct reference. When a tag is created, it records the exact SHA-1 hash of a specific commit. Once established, a tag permanently points to that exact commit and will never change or move, regardless of any subsequent commits made on any branch. It serves as an immutable bookmark for a specific point in the project's history, often used to mark release versions. Both lightweight tags and annotated tags share this characteristic of pointing directly and statically to a commit SHA-1.