A Moodle course is only as good as the content and materials added by the instructor. Course content is comprised of activities and resources.
A Resource is a file or other content that students can view (readings, web links, presentations, etc.).
An Activity is a course item that can be interacted with and graded.
For more information, see the Activities and Resources articles on Moodle Docs.
Adding Files to a Course
There are several methods you can use to add files and other resources to a course. The most common methods will be covered below. You must enable Editing Mode before you can use any of the file upload methods below.
Drag-and-drop: You may drag and drop files (doc, pdf, xls, ppt, etc.) directly from your computer into a topic section within a course. You can upload any single file that is 100MB or less in size. When using drag-and-drop, the files will be added to the end of the selected section and will display the file name. Once uploaded, files can be reordered via drag and drop. You can edit file names directly on the course page by clicking the pencil icon to the right of the file name. You can also drag and drop images (jpg, png, bmp, etc.) into your course.
File Picker allows you to directly upload a file or select a file from a connected file repository, such as Google Drive or WikiMedia. You can search for and add materials from these resources to your course. All of these repositories may be accessed through the File Picker.
Upload a File
On your file settings page, clicking the [Add] button will open the File Picker. Click on Upload a File in the File Picker to upload files, while setting the author and licensing of the file.
Private Files
This is a special storage area for each Moodle user that you will be able to access from any of your course sites. It's a great place to store files commonly shared amongst various courses you teach in Moodle.
Server Files
Server Files will allow you to access the file storage for other courses that you have access to in Moodle. If you suddenly decide that you want to add a file already used in another course site, you can go to Server Files > System and then navigate to your other course file to retrieve the document.
Repositories
It is possible for the Moodle administrator to enable repositories or other locations from which to pull content. Dropbox, Flickr, Google Docs and Youtube are examples of these.