Variables can be organized into several sections in the spreadsheet view.
Inputs section
The first section is always the Input section, this is not able to be renamed or deleted. Any variables that are in this section will show up in the Dashboard, and are able to be played with (i.e. adjusted) by viewers. If you don't want a variable to appear as an adjustable input, move it out of your model's Inputs section. Note: Model inputs can be in any section of a model!
Other sections
By default, there is one more section auto-created when you start a new model, named Calculations. However, you can delete or rename that section, add more sections, and reorder sections as you wish.