react - Difference between createMuiTheme and createTheme

As the title says. Both accept same kind of ThemeOptions object.

const theme = createMuiTheme({
  palette: {
    primary: {
      main: "#006400"
    },
    secondary: {
      main: "#ffa500"
    }
  }
});

const theme = createTheme({
  palette: {
    primary: {
      main: "#006400"
    },
    secondary: {
      main: "#ffa500"
    }
  }
});

Is createMuiTheme() only for applying styles to Mui components, and not my custom components?

If I want to create custom CSS classes, should I use makeStyles() instead?