Kraus sinks come automatically with the bottom grid, basket strainer(s) and their hand towel. That is why you are seeing this sink with the bottom grid in the pictures.

The bottom grid protects the bottom of the sink from wear from your utensils, pots & pans. Just think of when you're scrubbing a pan what it could do to the bottom of the sink. It also allows you to pour something down the drain with out it getting on plates that may be sitting in the sink waiting to be washed. But of course, you don't HAVE to use it. The grid is stainless steel too. So if it is fits, you can pop it in the dishwasher for a cleaning. Just take the rubbed feet and bumpers off before you do, otherwise they may melt.

is the grid solid stainless steel? Does it have a plastic coating on the grid.. I want to avoid that.

Yes. It is solid stainless steel. There isn't any plastic coating on it.