For many people, grout and mortar may seem like the same things. From a distance, they look very similar as well. However, they server slightly different purposes. For example, mortar is used as an adhesive to bind things together in construction. For example, mortar is used in between bricks in a building.
On the other hand, grout is used to fill in gaps but is not adhesive. For example, you may find it between sidewalk tiles. Grout is also made differently. This is especially true when you consider the number of specialty grouts that can be used for different projects. Grout tends to be made out of cement, water, sand, epoxy, acrylic, and polymer. Meanwhile, mortar only needs cement, sand, lime, and water.
Another large difference in the composition between grout and mortar is the amount of water used in the mixture. Grout uses more water while mortar uses less water. This means that mortar is stiffer than grout. Further, grout is also more viscous than mortar. Lastly, mortar comes in only a cement grey color. However, grout can come in a number of colors. This is one reason why grout is useful in so many contexts.