The Wall Tool is one of the most important tools to speed up your drawing from 2D to 3D, regardless of your profession. If you set up design layers correctly, the wall tool will give 3D for free. But that is only the start of what you can do with walls. Walls make it easy to draw complex plans, you can assign the wall components to classes (allowing you to create several viewports of the same walls that show different information), you can add data to the wall (and the wall has a lot of data already), and the wall is created in 3D (with different elevations for each component).
I have heard of some users that use lines to draw walls, and some users that use rectangles. But this is inefficient. When you draw using walls, it is easy to insert doors and windows (they will create the correct wall opening in the wall for you), they are easy to join together (there are joining tools), and when you move a wall, all the connected walls extend automatically (saving time).
We will be covering walls in the July workshop (book here) and manual (SST_1607).