Contribution can have different meanings in different context.
When contribution is applied to a product or product line, it means the difference between total sales revenue and total variable costs, or, on a per-unit basis, the difference between unit selling and the unit variable cost and may be expressed in percentage terms (contribution margin) or dollar terms (contribution per unit).
For further reading on small business financials, check out The Key Elements of the Financial Plan, as well as How to Read Your Business’s Balance Sheet, What Is an Income Statement? and How to Forecast Cash Flow.