A promotional item is merchandise given away free of charge to the public in an effort to promote a business or increase interest in, or sales of, a product. These items are also referred to by the slang terms schwag and tchotchke. (The latter is derived from a Yiddish word meaning “trinket”.) Promotional items are also used in politics to promote candidates and causes. Examples of promotional items include logo-branded t-shirts, caps, keychains, bumper stickers , pens, mints, etc. Collection of certain types of promotional items is a popular hobby.
Source : wikipedia