When you run mvn commands it can be aggregated which means single command you can issue multiple phase.
Example
mvn clean install
When you execute the command it cleans the project and install it again.
Another example
mvn clean dependency:copy-dependencies package
This command will clean the project, copy dependencies, and package the project (executing all phases up to package, of course).
How to generate the documentation?
mvn site
This command execute based on the information on the pom.xml. You can look at the documentation generated under target/site
Click on the site folder you see the bunch of documentation files.
Conclusion
So far we learnt the overall use cases of maven.