It’s basically government security for the president and vice president as well as all former ones because we have a long history of shooting our presidents. They also investigate counterfeiting which was their original job, they just happened to be formed shortly before the first successful presidential assassination
I suppose as a non American my idea of what the secret service actually is / does may be a little skewed by Hollywood
The secret service exists to prevent counterfeiting US money, as a side job they also protect a few people in government.
It’s basically government security for the president and vice president as well as all former ones because we have a long history of shooting our presidents. They also investigate counterfeiting which was their original job, they just happened to be formed shortly before the first successful presidential assassination