What is the difference between git push origin and git push origin master

The default action of git push and git push origin has changed since git version 1.7.11:

• Before 1.7.11, git push by default pushes all branches that also exist remotely with the same name.

• Since 1.7.11, git push by default pushes the current branch to a remote branch with the same name.

Before and after version 1.7.11, the default behavior can be configured with the push.default configuration option. This configuration option has been introduced in git version 1.6.3.