A paper advertisement or a folded brochure is called a leaflet. To spread the word that your band is playing tonight, you could hand out leaflets.
Most leaflets are free, part of their purpose being to attract an audience or customers, or to spread specific information or propaganda. You can also use this word to mean "small section of a leaf," particularly on a "compound leaf," which is made up of several leaflets, like the leaf of the ash tree. This botanical meaning is the original one — the "pamphlet" meaning arose in the 1800s, from leaf, or "page of a book."