what does make styles mean in material ui in reactr code example

Example 1: material ui common styles

const useStyles = makeStyles({
  root: {
    color: 'red',
    '& p': {
      color: 'green',
      '& span': {
        color: 'blue'
      }
    }
  },
});

Example 2: material ui common styles

const useStyles = makeStyles({
  // style rule
  foo: props => ({
    backgroundColor: props.backgroundColor,
  }),
  bar: {
    // CSS property
    color: props => props.color,
  },
});

function MyComponent() {
  // Simulated props for the purpose of the example
  const props = { backgroundColor: 'black', color: 'white' };
  // Pass the props as the first argument of useStyles()
  const classes = useStyles(props);

  return <div className={`${classes.foo} ${classes.bar}`} />
}