what is the difference between staging area and repository?

[Tim Crall · Accepted solution]

The staging area holds changes that you have made to your source files and have staged (using "git add") but have not yet committed.  It allows you to collect all the changes that you want to commit together in one place before committing.  Most of the time it's a bit of an unnecessary step as you'll just want to commit all your changes (which you can do with "git commit -a") but sometimes you may have made changes that do not logically belong together in a single commit.  In this case you can stage only certain changed files (using "git add") while leaving other changed files unstaged.  When you do a "git commit", only the staged changes will be committed.  You can use "git status" to see which files contain changes and whether or not they are staged for commit.

[Johannes Kilian]

The staging area even offers more levels of adding "things":

• You can also add just parts/single lines of a changed files to the staging area while other parts/lines are left out.

For example: Having a file, where you fixed two separated bugs without commiting, you are able to stage only the hunks/lines concerning the fix of the first bug for your first commit. After this you might add the remaining changes (second bugfix) to the staging area - and perform a second commit.

Consider Statig area as a container to collect all logically mated changes for your next commit from your unordered unrelated uncommitted changes in your sandbox ...