Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.
Guarantees freedom of speech, religion, press (aka media and reporting), the right to PEACEABLY assemble and the right to petition the government to fix the things they are responsible for.
While there are obviously some restrictions such as not being able to slander someone, the freedom of speech means you can say whatever you want. While you can say whatever you want, you are not protected from backlash or protected from the consequences of your words. The important thing to keep in mind is that nice and polite speech has never needed to be protected. However, offensive and disagreeable speech has. Some may also refer to this as "Hate Speech", even though "Hate Speech" really only lives outside of the US, because the US is the only country in the world while guarantees the protection of free speech.
Further more, it is important to understand that freedom of speech also includes your intellectual property like plans and in todays world, code. If you write code for software and post it; its speech. If you write code creating a product and post it; speech. Twitter; Speech. Facebook; speech. Now, its important to also note that places like Twitter and Facebook are private companies with their own rules for what is and is not allowed on their platforms. If they want to take your code or posts down because it breaks their rules, they are allowed to. However, they must apply those standards EQUALLY across the board, regardless of political party affiliation, sex, religion, etc.