The Canadian Intellectual Property Office defines a trade-mark as:

A trade-mark is a word (or words), a design, or a combination of these, used to identify the goods or services of one person or organization and to distinguish these goods or services from those of others in the marketplace.

This can be further broken down into three different types of trade-marks.

• An ordinary mark can be words or a design or a combination of both that is used to distinguish a product or service from others in the marketplace. An example of this would be the words “Coca-Cola” or the famous Coca-Cola written in script on the side of the bottle.
• A certification mark is used by an individual or organization to identify products that meet a certain standard. An example of this would be the Canadian Standards Association (CSA) logo seen on many of our products.
• A distinguishing guise consists of the shape of a product or its container or a mode of packaging goods. The famous glass Coca-Cola Contour Bottle is an example of this.

Trade-marks are powerful because they prevent someone from trying to profit off an established brand. If I was to make my own cola drink and try to call it Coca-Cola, the Coca-Cola Company would have the right take me to court to defend their trademark. This protection is very valuable because it prevents counterfeit goods of dubious quality from flooding the marketplace and weakening an established brand.