Their actual name is just frisk.
They have a special ability which used to belong to their frienemy flowey, its the power to save a point in time so they can load it later to go back on mistakes. Sans knows it exists but flowey can remember from separate resets unlike anyone, despite technically being a god. They never kill anyone. Or even harm them THAT bad. Although they like fighting and making playful threats. They are overly nice to everyone. And even like mocking people (Especially flowey)