They've always been around in some flavor or another, but they (like many once niche shticks) blew up with the internet.

spitball Cliff Notes: "I'm not an American citizen bound by American laws, I am an American National born on US soil. I have a right to travel, which I am doing in my conveyance (vehicle) therefore you cannot apply driving laws to me for I am traveling, not driving." Basically, they think there's a secret set of laws/combination of laws that allows them to exist "outside" of the system without engaging with it's various parts (usually driving/car reg laws and taxes, but can include things like debt, court, etc)

extra nutter cliffnotes: "The name in all caps on your birth certificate is a corporation/strawman/legal fiction owned by the US govt via which you interact and do business with the govt, whereas your true name is your first and last with only the first capitalized as proper English grammar dictates. Taxes and other govt business are not done with me John Doe, they are done with the corporation of JOHN DOE, and I as a (American National/free man/pick a term) am not responsible for the tax obligations or other legal business the corporation of JOHN DOE has with the government."

TLDR Cliff Notes: "I can not be bound by American laws because I never agreed to be governed by American laws."

It began being known by that name in a white supremacist group ideology called Christian Identity as part of a group called the Posse Comitatus in 1971 in the US, but had its roots in general anti-government groups even earlier than that. It grew much more with the American farm crisis of the 80s and 90s to begin to exclude the white supremacists from its members. In the 90s the ideology was adopted by the Moorish Science Temple which is why so many of them are now black. It exists in other countries too, Australia has a lot of them, called Freeman on the Land. It has expanded greatly in the 2000s due to recession and mortgage crisis. The ideology meshes with Qanon often; a sovcit group called the Oath Enforcers showed up to the insurrection to support Trump for example. It can now be found in 26 countries, even Singapore.

Thungs like Qanon and antivaxxers and the COVID pandemic have attracted many more people to it, sovcits are of course animask and antivax. They HATE Jews.

Basically sovcits believe they are private people not bound by government laws. They will not have licenses or plates, do not pay taxes, and believe a lot of what is called pseudolsw..they "paper terrorize" the courts routinely.

They are crazy funny in my posts but they are capable of violence and many are in militias.