Though you can use the terms "brochure" and "information sheet" to mean the same type of document, there is a general agreement that a brochure serves as a marketing tool, and an information sheet, or fact sheet as many call it, is more for purely informational purposes. There are varying differences in features and format as well.
Generally speaking, the purpose of a brochure is to sell or market a product or service. An information sheet focuses on providing information, and this may be about a product or a company or it could be about something else, such as a disease or a government program. A brochure can, and often does, provide information as a way to sell the product in question, but its primary purpose is marketing.
Often a brochure is a single sheet of paper that you fold to produce many smaller panels that you format and read as separate pages. A brochure will have a cover, and inside and a back. It might have overlapping flaps, so you open one fold and then another before you get to the center. Sometimes the back panel of a brochure is a mailing panel, to which you affix postage and an address label. In contrast, an information sheet is usually a flat page, or it may be several pages stapled together, but they are less likely to be formatted with a fold or folds.
The content of a brochure and fact sheet may be similar. However, a well-written brochure has some important features: the cover will grab the reader's attention and get her to read the rest of the text. Then, the inside content will show the reader why she needs the product or service being marketed. It should end with a call to action, suggesting the reader buy the product, call to make an appointment for a sales call or whatever the marketer wants the reader to do.
Each of these document styles is rather loosely translated, and none of this information is a hard-and-fast rule. Some use these terms interchangeably, and each format is really what you make of it. Also, each can be fancy and expensive, designed by a professional designer and printed on thick, glossy paper with full color photographs. Or they can be plain, black and white with simple fonts and no illustrations or photos. It depends on the purpose and your budget.