What's the difference between mvn:deploy and mvn:install commands?

mvn:install copies your packaged Maven module to your local repository (by default, in ~/.m2/repository), to be accessed by other local Maven builds.

mvn:deploy uploads your packaged Maven module to another (usually remote) repository, to be accessed by other, not necessarily local, Maven builds.

See the documentation for the build lifecycle for more info.

The install phase is responsible for the installation of artifacts into local caching repositories. This basically applies to the Maven repository, but a well-known example is also the OSGi Bundle Repository supported by maven-bundle-plugin.

The deploy phase is responsible for the installation of artifacts into published repositories. This usually applies to remote repositories, but is could perfectly be a local repository exposed to the outside world.

As all Maven phases, you can do with them anything you want. You can shuffle plugin phases as you see fit, but the above semantics is the conventional one and you should stick to it in order to be consistent with the default phases of other plugins' goals.

mvn:deploy performs deployment to remote reposiory/environment, mvn:install installs all compiled packages to a local repository making them available to other builds performed on the local machine.