Entrepreneurs on BBC's Dragon's Den usually offer equity in exchange for funding.
Equity means an ownership share in a company. During a pitch, an entrepreneur states how much money is wanted and what percentage of the business is being offered. The Dragons then assess the implied valuation, the company's sales and prospects, and whether the requested ownership is appropriate for the risk.
A deal may involve one Dragon or several Dragons, and the final percentage can change during negotiation. A televised offer is not automatically a completed investment: due diligence and legal work normally follow before a transaction can be finalised.
The arrangement is different from a salary, which pays someone for employment, and from a loan, which normally has to be repaid with interest. It is also different from a patent, which protects an invention. Because the show centres on ownership and valuation, equity is the canonical term for the stake offered to the investors.