In Dragons' Den, the percentage of a business offered to an investor is called equity.
Equity represents ownership in a company. When an entrepreneur offers 10% equity for an investment, the proposed deal would give the investor a 10% ownership stake, subject to the final terms agreed in the den. The money requested and the percentage offered together imply a valuation for the whole business.
For example, asking for £50,000 for 10% equity implies a pre-money valuation of £450,000 if the investment is treated as new money entering the company, although television negotiations and deal structures can become more complicated. Equity is different from revenue, which is money earned from sales, and from a dividend, which is a payment to shareholders.
A verbal agreement in the den is not necessarily the end of the process. Due diligence and legal negotiations can change or prevent a deal after filming.