"The grid" is literally the thing that joins battery parks (eg: the massive one in Adelaide South Australia) to rooftop providers, wind farms, household and commercial electricity consumers

"Investing in the grid" means expanding capacity in order to meet increased electricity demands as electric vehicles replace fosil fuel vehicles and increasing switching and grid intelligence to better handle a more distributed supply and demand.

More solar + more batteries and thermal storage + better grid are all things that grow hand in hand.

Of course investment in the grid is required to meet large scale population demands.

Yes you can use batteries.

But you can also invest in the grid and have excess energy shifted to other regions that can make use of it.

You could also just waste the power. Why not?

It might be cheaper to waste it than to reclaim it, if integrating that source to the grid is too expensive. When generation significantly exceeds demand, that scenario will happen.