What does '& > * + *' mean in JSX (CSS)?

In material UI, there are lines of JSX in progressbar demo like this:

'& > * + *': {        marginTop: theme.spacing(2),      },  

What does the '& > * + *' mean here?

https://stackoverflow.com/questions/66863796/what-does-mean-in-jsx-css March 30, 2021 at 09:55AM