git commit

Create a new commit using staged changes

git commit -m 'my commit message'

Create a new commit using staged changes and given message

git commit -a -m 'my commit message'

create a new commit after staging changes in working directory (except untracked files) and give commit message

git commit -a -S -m 'my commit message'

create a new commit after staging changes in working directory (except untracked files) and given commit message, also sign the commit, using gpg

git commit -amend 

drops last commit and creates a new commit using current statging area content and msg of last last commit. Allows you to edit commit msg, changes in your last commit.