The command you're searching for is git diff.
git diff - Shows changes between different commits like their commit ID, commit and working tree, etc
Here are some of the choices it exposes that you can use
git diff (no parameters)
Print out differences between your working directory and the index.
git diff --cached:
Print out variations between the index and HEAD (current commit).
git diff HEAD:
Print out differences between your working directory and the HEAD.
git diff --name-only
Show only names of changed files.
git diff --name-status
Show only names and status of changed files.
git diff --color-words
Word by word diff rather than line by line.