Moodle has a fairly comprehensive set of ways to access Moodle. Yes, there is a "desktop app," and a "mobile app." However, these "apps" are meant to be used in conjunction with a "Moodle server" as far as I know. So the first step is to figure out where your "server" is going to be. Without your Moodle on a server, I believe that your Moodle Desktop Site will be blank.
For example, you might want to consider experimenting with the free MoodleCloud server. This is where you can create courses and add users. I am not sure if the Moodle Desktop App can be used with MoodleCloud, I think it can, but others here will confirm.
Yes, getting your own "server" up and running is a bit technical, maybe more than you want to handle right now. You might want to explore "Moodle Partners" who make their business on providing Moodle on "servers."
You might want to search Google for "What is Moodle?" Also, on LinkedIn Learning (Lynda.com) there are some "courses" on Moodle, which although may not be most current, will provide you some background. And there are some decent books.