There are so many things that you can do with Home Assistant and the project keeps expanding. There is talk about machine learning integration and new user account control in the development pipeline. Here are some links to documentation on the Home Assistant web site.
The user interface that is used for Home Assistant is called Lovelace and not only is it nice looking, but it easy easy to customize through any computer web browser.
There is a tool that can be used to create some rather complex Automations in the Configuration menu. This is the easiest way to create some rather complex automations without using Node-RED or editing YAML files in the automations.yaml file.
Scripts will allow you to use one command to do a bunch of things at once. This can be handy if you have a series of actions that will be reused in automations.
These tools are very useful for testing and troubleshooting devices, but also for seeing what data is needed for automations and scripts. The Services tool is very helpful for creating and testing the JSON formatted Service Data used with more complex devices like lights and media players.