Kitchen Tile Backsplash/ Wall
They are lugs. If you look at the tile from the side you will see besides the lugs the tile itself is slanted towards the face starting from the lugs. This is what create the grout line. Also how the tile person actually grouts will later the size of the grout line. If a tile person over cleans his grout the grout gets washed out of the larger portion of the space and into the narrower part of the "V". You can have the same tile spaced using the lugs and have different size grout lines. With todays waterproofing systems and advanced thinnest the grout is just decorative especially with butt installed tiles. With darker grout look into Mapei Flexcolor grout. It has a sanded grout appearance and is more difficult to apply on vertical surfaces but it gives a very durable finish that has a dead on color that can even be touched up and still have the same color. Dark color cementitious grouts are notorious for color issues especially if the installer over washes or doesn't mix as per instructions. The Flexcolor is premixed and the color is accurate throughout. There will be sand everywhere but in the end the extra effort is worth it. With the Flexcolor I would use 1/16th spacers but remember it will give you a larger grout line as the tile itself already has 1/16 built into it. The larger line allows the sanded type grout a space to get into. No it isn't regular sanded grout it isn't even sand it just has a sanded appearance and feel to it. 2 different products.