Hello there In response to your final comment, you have obviously managed to ask questions so that is good.
You might like to take a look a the About Moodle FAQ which might answer some of your questions.
Moodle is the name for free, open source software which anyone can download and use.
MoodleCloud is a product made by the people who make the Moodle software (usually known as 'Moodle HQ') and they offer this as an already set up version of Moodle that you can use to practise with so you don't need technical skills and time to download it yourself.
Moodle.net is in flux at the moment. The current site moodle.net is a repository of Moodle courses and course content for anyone to contribute to and add to their Moodle site. MoodleNet is its successor and enhanced version, about which you can read more here: MoodleNet
There is also LearnMoodle if you want to learn how to use Moodle as a teacher (not admin) which is a course still open for sign up at the moment if you are interested.