The easiest way to imagine it is like this: investors contribute money and are almost certain that it will simply vanish, as the business they have chosen are unlikely to become established. But in case it does succeed, they can make a huge profit if the company turns out to be, for example, the new "Yandex". The risks are high, but the potential profit is huge.
It is important to understand that not every business is a venture project. For example, a "Yandex" equivalent can be considered one, but a new cafe can’t.
The difference lies in the potential of the business project. If the new "Yandex" is successful, it will be able to scale and become popular all over the world, which guarantees a huge income.
A cafe can’t do that. In this case, for example, one will have to open cafes in other countries, spend money on rental and recruitment of personnel, etc. Business development will be linear, not exponential. That’s why you can’t consider cafe to be a venture project.