Assignments:
There are two basic types of assignments--online and offline.
Here is a flow chart of how assignments work in Moodle.

flowchart
Directories:
Directories can display files. It's a good idea to setup a file structure for a course early on, even if you don't display directories. Otherwise your course documents might start looking like your desktop


Directory of Course Files for Blended Moodle

Activity: Watch Atomic Learning Tutorials

Task: Create Assignments in Your Moodle

Task: Create File Structure for Course

Forum: Assignments in Moodle