A more thorough explanation:

Definition: Infringement of trademark occurs when a person uses another's trademark or service mark without permission or uses a substantially similar mark on competing or related goods and services. The success of a lawsuit to stop the infringement depends on whether the defendant's use causes confusion in the average consumer. If a court determines that confusion is likely, the owner of the original mark can prevent the second user's use of the infringing mark and sometimes collect damages.

For example, if a company creates a logo that is very similar to another company's logo, and the logos are used on similar products, it could be considered trademark infringement. In the case of McLean v. Fleming, the court found trademark infringement for a pill that was not identical to a trademarked pill but was so substantially similar that it was "calculated to mislead and deceive."

Under the modern federal statutory regime, the Lanham Act governs federal trademarks. It allows an infringement action where any person, without the consent of the registrant, uses a reproduction, counterfeit, copy, or colorable imitation of a registered mark in connection with the sale, offering for sale, distribution, or advertising of any goods or services on or in connection with which such use is likely to cause confusion, or to cause mistake, or to deceive.

While injunctive relief for the victim of trademark infringement is available, the Lanham Act takes steps to limit the injunctive actions courts may take. For example, in the case that the alleged infringer only prints the mark, the only injunctive relief available is to prevent future printing.

Overall, trademark infringement occurs when someone uses a trademark or service mark without permission or uses a substantially similar mark on competing or related goods and services, causing confusion for consumers. The Lanham Act governs federal trademarks and allows for legal action to be taken against infringers.