Commercial speech has been defined by the Supreme Court as speech where the speaker is more likely to be engaged in commerce, where the intended audience is commercial or actual or potential consumers, and where the content of the message is commercial in character.
Commercial speech, such as advertisments, has been ruled by the Supreme Court to be entitled to less protection under the First Amendment than noncommerical speech. Under the First Amendment, noncommercial speech is entitled to full protection, and any sort of content-based regulation is only valid if it can withstand strict scrutiny. However, commerical speech is not given such deference. For a content-based regulation of commercial speech to be valid, it only must withstand intermediate scrutiny.
Additionally, commercial speech that is false or misleading is not entitled to any protection under the First Amendment, and therefore can be prohibited entirely.