Commonly, trademarks are brand names and/or designs that are applied to products or used in connection with services. There are actually four different types of "marks" which we commonly think of under the term "trademark." These are trademarks, service marks, certification marks and collective marks.
The shape of the packaging can be a trademark. Even color combinations that are found on products may be trademarked as "trade dress."
TIP: When you have come up with the perfect trademark idea for your business, you should check to make sure that it is not already taken by someone else. You can reserve the rights to your trademark through actual use of the mark or by registering with the USPTO.