The court opinion is 70 pages long, they define it multiple times. One example is: "All manner of speech—from “pictures, films, paintings, drawings, and engravings,” to “oral utterance and the printed word”—qualify for the First Amendment’s protections; no less can hold true when it comes to speech like Ms. Smith’s conveyed over the Internet"

Essentially it's already been established that the government can't enforce rules on what products someone makes, but can enforce who they sell that product to (not disallowing protected classes). The state of Colorado was arguing that making websites was a standard product that could be modified to be sold to anyone, while ms Smith was arguing that each website was a unique product that had freedom of speech. The only thing the court decided was that websites should be considered speech, so they fell under the same rules that have already applied to paintings and songs, instead of the rules that apply to groceries and car sales