A kiosk is a very small, very simple building out of which things are sold. You might find kiosks in the street, selling newspapers, cigarettes, soft drinks, lottery tickets, and suchlike. It's a couple of metres high by a couple of metres wide. There's usually just enough room inside a kiosk for a salesperson and his merchandise. Unlike a market stall - which is put up each day and taken down again - a kiosk is a relatively permanent structure, even though it's very basic.
It's a Turkish word, originally from Persian, which has found its way into many other languages in the world. The meaning above is how 'kiosk' usually used in English.
I hope that answers your question.