git diff HEAD

This command contrasts the contents of the files in your current working directory with those found in the last commit (referred to as HEAD).

It effectively gives you a summary of all the changes that you've made but not yet committed to the repository.

It includes information such as additions (marked with +) and subtractions (recognized by -). For comparing with other commits or branches, simply replace HEAD with the desired commit hash or branch name. For example, git diff HEAD~1 compares with one commit before the last.

Moreover, you can use --stat to see a summary instead of the full diff, or --color-words to see changes at the word level, instead of by line.