The terms cement, concrete, and mortar can be confusing to beginning builders, but the basic difference is that cement is a fine binding powder (which is never used alone), mortar is composed of cement and sand, and concrete is composed of cement, sand, and gravel. In addition to the differences in their composition, they have vastly different uses. Even trades people who work with these materials daily can colloquially confuse these terms since cement is frequently used to mean concrete.
Cement is the binding element in both concrete and mortar. It is made most commonly of limestone, clay, shells, silica sand and other materials. These materials are crushed and then combined with other ingredients (including iron ore), and then heated to about 2,700 Fahrenheit. This material, called Clinker, is ground into a fine powder.
You might see cement referred to as portland cement. This is because it was first made in the 1800s in England by a mason, Joseph Aspdin of Leeds, who likened the color to the stone from the quarries on the island of Portland off the coast of England.
Today, portland cement remains the most common cement used. It is a type of "hydraulic" cement, which simply means that it will set and harden when combined with water.
Concrete is commonly used across the world as a strong foundation and infrastructure for almost any type of building. Its unique characteristic is that it starts out as a simple, dry mixture, becomes a liquid, flexible material capable of forming into any mold or shape, and ends up as the hard-as-rock material we know as concrete.
Concrete is composed of cement, sand, and gravel or other fine and coarse aggregate. The addition of water activates the cement, which is the element responsible for binding the mix together to form one solid object.
You can purchase ready-made concrete mixes in bags that combine cement, sand, and gravel so that all you need to do is add water.
These are useful for small projects, such as anchoring fence posts or other fixtures. For large projects, you can either buy bags of cement, and mix them with sand and gravel yourself, using a wheelbarrow or other large container, or order premixed concrete and have it delivered and poured.
Mortar is composed of cement and sand. When water is mixed in with this product, the cement is activated. Whereas concrete can stand alone, mortar is used to hold together bricks, stones or other such hardscape components. Cement mixing, therefore, properly speaking, refers to using cement in the mixing of mortar or concrete.
Mortar is sometimes used between bricks in the building of brick patios, although it is not always used in such cases. For instance, in northern climes, where mortar could well crack in winter, the bricks may be simply fitted tightly against each other, or incorporate sand between them.