There are many subtle and not so subtle differences between mortar and grout. Some of those differences are explained below.
The concentration level of water in grout is different than what you would find in a mortar mixture. Grout, for example, has enough water in the mixture so that you can pour it from one location to another. However, it does not have an overwhelming amount of water that would cause the ingredients to separate. Mortar, as compared to grout, does not have as much water in the mixture.
Mortar is much stiffer of a product than grout. Because of this property, grout works best around things like steel and small spaces. Mortar, by contrast, is used for filling large joints.
Types of Uses
Generally, grout is used to fill in between a tile job. Mortar, on the other hand, is used in all sorts of different building applications, especially when it comes to laying bricks.
Mortar comes in only a couple of colors, most of which is sandy white. Grout can be found in many different pigments to apply to different projects that need to fit in with a certain decor.