Hi could someone please help explain this equation to me?

Note that multiplying the units W m −2 by m 2 gives W because:

I get that (for example) 1370 W m$\displaystyle ^-2$ is the same as saying 1370 W per metre squared, but I'm not very sure what a m$\displaystyle ^-2$ on it's own is? If it's not “per meter squared” then perhaps it represents 'one metre to the minus 2”?

However if I were reading this literally from what I've learned so far the $\displaystyle m^-2 $ x $\displaystyle m^2$ part would read per metre squared times (one) metre squared (which doesn't seem to make any sense.) Of course getting lost here means I'm lost on the rest of the equation too.

I admit I'm a bit stuck here.