Some call it a “grill” and some call it a “grid.” 
What they are referring to, is the custom made, custom fit piece that sits at the bottom of your sink. The best advice I could give you, is to make sure the sink model you are buying also offers this custom fit accessory. Some manufacturers “package” the sink along with the grid. Some, you have to purchase it separately. Either way, get one! Here’s why:
1. It protects the bottom of your sink. No matter what material your sink will be made of, it will not be indestructible. Yes, even stainless steel sinks can be scratched or marked up by utensils, pots and pans and whatever else that may go in your sink. The grid will keep these items off of the bottom of the sink, maintaining the “new” look longer than with out. Plus, you can always replace the grid in the future, if need be.
2. Draining is a cinch. For those men in your life who like to leave the dirty dishes sitting in the sink, you do not have to worry when it comes to draining. When it comes time to drain your pasta, or oil, the liquid will by pass the items sitting on the grid, and run along the bottom of the sink to the drain.
3. Adds a custom look. You want to look for a grid that is formed fitted to the 
sink model you chose. It will fit perfectly with in the sink, and not be able to shift or move. Therefore the drain will always be accessible through the custom hole with in the grid.
4. They are easy to clean. If your grid is small enough, you can just pop off the rubber feet and side protectors, and put it in the dishwasher for an easy clean. If you are blessed enough to have a larger sink/grid, you can just use soap and water or a non abrasive cleaner to wipe down the grid. Or, just soak it with in your sink!
5. Aids in cleaning fruits and vegetables. The bottom of the sink is not where you want your food to rest. The grid keeps your food off of the bottom while you’re rinsing.
So now that you are fully on board with buying a grid, there are a couple of things you should be aware about when choosing your sink/grid.
1. The design of the gridding. Some grids only have some horizontal lines, like pictured here. I find that as this design is effective on some levels. But the pattern leaves big spaces, where your silverware can slip between the grid and onto the
bottom of the sink. I’d prefer a design that is more checkered, where commonly used items won’t fit between the spaces.
2. No Coating. Some manufacturers like to put a clear coating of some sort on the metal of the grid. I do not like this for a couple of reasons. One, it makes the grid look dirty faster. Two, hot water and hot pots can sometimes melt this coating, ruining your grid. Look for a grid that is stainless steel through and through.
3. Color of Feet & Side Bumpers. Black! You want these to be black. I’ve lived with the clear AND white feet. They get miss colored, and stained. The black feet do not do this. Here’s another tip, if you are going to wash your grid in the dishwasher, take these plastic pieces off! They may melt, or get lost during the wash!
There you have it! More information then you may have wanted about a sink bottom grid. But trust me, once you have one, it’s something you won’t want to live with out. And yes, it is okay for a sink grid to have weight in your sink model decision. Think about how often you are going to remodel in your life time. You always want to do it right the first time.