In Dragon's Den, the entrepreneurs who invest their own money are called dragons.
The term comes from the programme's title and describes the experienced business people seated on the panel. Entrepreneurs enter the den to present a product or company, state how much funding they want, and offer a percentage of their business in return.
A dragon may make an offer alone, or several dragons may join together. The investment is normally negotiated around valuation, equity and the conditions attached to the deal. A televised agreement is not necessarily the final completed investment, because both sides still carry out due diligence after filming.
The word “sharks” is a common mix-up because that is the panel name used by the US programme Shark Tank. In the British format, “dragons” is the canonical term, even when a pitch attracts several investors.