1. What is a Commit?

A commit is a saved snapshot of staged changes in the local Git repository.

git add .
git commit -m "Added login feature"

Flow:

Working Directory
      ↓ git add
Staging Area
      ↓ git commit
Local Repository

Each commit contains information such as the changes, author, date/time, message, and a unique commit hash.

Interview Answer

A commit is a snapshot of staged changes saved in the local Git repository. It creates a point in the project history that we can track or return to later.

2. What is a Commit Hash?

A commit hash is a unique identifier generated by Git for each commit.

Example:

a4f82c91d5e7...

View commits using:

git log

You can use the hash to identify a specific commit:

git show a4f82c9

Key Point

Commit
  ├── Hash
  ├── Author
  ├── Date
  ├── Message
  └── Changes

Interview Answer

A commit hash is a unique identifier for a Git commit. We use it to identify, inspect, compare, or reference a particular commit in the repository history.

3. What is HEAD in Git?

HEAD is a reference to the commit currently checked out. Normally, it points through the current branch to that branch's latest commit.

Example:

A ← B ← C
        ↑
      main
        ↑
       HEAD

Here, HEAD indicates that we are currently on main, whose latest commit is C.

Check the current branch:

git status

Important Point

After a new commit:

Before: A ← B ← C  ← HEAD
                   |
                  main

After:  A ← B ← C ← D  ← HEAD
                       |
                      main

Interview Answer

HEAD represents the currently checked-out position in Git. Normally, it points to the current branch, which in turn points to its latest commit. When we create a new commit, the current branch and HEAD move forward to that commit.