While your first thought might be that it sounds like it defeats the purpose of an elevator, we mean it has open doorways, but no closing doors. Basically, think of a nonstop ferris wheel. It’s called a paternoster, and today there aren’t many of it left.
It’s a passenger elevator that is made up of a chain of open compartments that move slowly in a constant loop. The benefit is that, like an escalator, people can get on at any time. People can also get off at any floor without having to select it or wait for others to reach their floors. The drawbacks are obviously safety related, because such a mechanism is pretty dangerous.
Because of the safety issues, most of the lifts are now gone. A few are still around though, like the one in the Arts Tower at the University of Sheffield in the UK.