Are you referring to the grout? If so, use a standard grout. The type of grout depends on the tile and the size of the grout joint. You can't use unsanded if the grout joint is greater than 1/8" or it will have shrinkage cracks. You can force sanded grout into smaller joints, but it's harder. Sanded grout is stronger, but some people don't like the rougher look. Don't use the stuff in a spray can, or premixed. It doesn't last, and some of them can make you sick while the solvents evaporate. An alternative that's more expensive would be to use an epoxy grout. This looks smoother and is shinier. You can put weird stuff into it that can make it glow in the dark, and get different, brighter colors. An epoxy grout doesn't need a sealer. You must clean up properly, or you'll have a big, sticky mess on the tile. You must follow the instructions carefully. Check out
www.johnbridge.com for help on tiling.