There are 3 basic sealers:
Clear penetrating sealer, which as its name states, is clear & doesn’t darken or add sheen to grout.
Clear sealer with Matte to Gloss finish, these product are thicker & will darken most grouts ( a shade or 2 at most ) and leave a sheen on surface to match your tiles .....
Color sealers, acrylic based with polymers & fillers, used when grout is stained or you simply want a new look. Unlike Dyes or Stains, which wash away over time, our color sealers are extremely durable.