Grout
Cement-based filler installed between tile joints. Sanded (wider joints) or unsanded (narrow joints).
Grout is the filler that goes between tiles after thinset has cured. Sanded grout (with sand aggregate) is used for joints 1/8" and wider. Unsanded grout is used for joints under 1/8" and for polished stone.
Color choice is one of the most visible decisions on a tile install — confirm with the customer before opening the bucket. Pre-mixed urethane and epoxy grouts cost more but resist staining and don't need sealing.
Standard cement grout needs to be sealed within 72 hours of installation and re-sealed every 1-3 years. Add sealer and sealing labor as a line item — it's a real cost and customers often want it included.