According to the American Marketing Association, a brand is a “name, term, sign, symbol, or design, or a combination of them intended to identify the goods and services of one seller or group of sellers and to differrentiate them from those of the competition”.
One simple way of distinguishing them used to be whether they are offline or online.
More and more cross-overs is blurring the line.
Example include Yahoo, Egghead.com, Wingspanbank, Schwab, Ragu.