Grid

What exactly does this "grid" mean?

And we must be connected to the grid at all times. We take our smartphones and laptops with us on vacation. We go through our email at restaurants. Or our online bank accounts while walking in the park.

I have a vague idea of it: judging from the context, here it seems to mean those "screens." But I don't find in my dictionaries any definition of "grid" related to such things.