There are three standard types of grout for tile jobs: non-sanded, sanded and epoxy. The type of grout used in a shower depends on the size and type of tile.
Non-sanded (or un-sanded) grout is for use in grout lines smaller than 1/8 inch wide, as non-sanded grout shrinks enough to pull away from tiles with larger grout lines. Sanded grout is used for grout lines that are 1/8 inch or wider. Epoxy grout can be used with any type of tile, regardless of grout line width. It is also stain resistant and waterproof, making it ideal to use in a shower for those who prefer a grout without sand.