When to use calk and when to use grout ?

When doing tile in tub area, caulk inside corners and tub to tile with caulking same color as grout. Same with shower stall.

Caulk tub to floor tile.

If u need more info,expand on your question.

Good luck

Chuck

Consider the material types the tile is adjacent to and the potential for expansion/contract over the course of the year (due to temperature/humidity).
For example – when I had tile adjacent to a hardwood floor I used a expansion molding with caulk against the tile (as that will likely move). The same is true for counter tops and bath areas.

If you have the time and are concerned about matching the grout, colored caulk can be used.

Caulk flexes, grout does not.