What is mortar?
Mortar Definition– A substance used to bind building materials together, particularly brick or stone.
Ideal Home Garden Explains
Mortar is typically made with sand, water and either lime or cement, and is used as a paste applied between two pieces of building material. As the mortar dries, it hardens and creates a firm bond between the two pieces. Mortar is most often used in masonry, plaster work and surfacing.