Coffee is not only a bean. The same plant also has leaves — and in several places where coffee grows, those leaves have been dried, boiled, smoked, or brewed and shared as their own beverage, separate from the bean entirely.
Coffee originates in the highlands of Ethiopia, where the plant still grows wild in forest understory. Leaf preparations such as Engere, Kuti, and Chemo are documented there. A similar tradition, Kawa Daun, exists in the highlands of West Sumatra, Indonesia.
These aren't the only places, and they aren't presented here as a list to memorise — just as a few starting points, each with its own page if you'd like to read further.
It depends on the leaf and how it's prepared — but some words that come up often:
If you'd like to know more about why — which compounds, which processing choices — The Sensory Landscape of Coffee Leaf goes into this in more detail.
It isn't coffee without the beans, and it isn't tea from the tea plant (Camellia sinensis) either. It's a different part of the coffee plant, with its own character — sometimes closer to one, sometimes closer to the other, and sometimes its own thing entirely.
Because traditional use exists and is documented, scientific interest in coffee leaf is growing, and — compared to the bean, which has been processed and studied for centuries — the leaf's processing possibilities remain comparatively unexplored. That combination seemed worth taking seriously.
Wherever you're curious about. A few directions: