Variable expenses are those expenses that track directly with sales. If sales stop they stop. These are expenses like supplies used to support in the making of your product or doing your service. Such things as shipping cost for raw materials for your product or service. If you have no sales then you're not going to be purchasing materials so your shipping cost for those materials will stop as well. As an example, if you have a lawn mowing business and there are no lawns to mow, then you wouldn't be buying gasoline to travel to your lawn mowing site. These kinds of things are variable expenses. If you're producing a product, it would include supplies used to produce that product like sand paper, glue, finishing materials, cutting tools, etc.
They are like fingerprints; no two are alike, even within the same organization. One further point, opinions about what makes a good finished product are like noses_everybody has one. The ones that work and prove to be executable are the best. With this in mind, let me offer my views about business plans at a macro level having written a sizeable number of plans for internal and external applications. One other point, a business plan can build a team quicker than any formal team building activity.