A brand is a name, term, design, symbol or any other feature that identifies one seller's good or service as distinct from those of other sellers.

Marketing is the process of identifying customer needs and determining how best to meet those needs.  It refers to overall activities a company undertakes to promote the buying or selling of a product, service, or good.  Marketers may direct their product to other businesses or directly to consumers.

Advertising is a component of marketing that focuses on promoting a company (and it's products or services) through paid channels.