Masonry is the term used when structures are built from individual units bound together with mortar. Masonry blocks are often made of: concrete (also known as CMU's), clay (aka brick), stone, and even glass. Similar to concrete design, masonry structures can vary significantly depending on the type of masonry being used, type of mortar being used, whether or not structural reinforcement (rebar) is present).
Unfilled masonry is generally used for compression type structures when little lateral forces (e.g. earthquake) will act on the structure. If the masonry units are filled with concrete, steel reinforcement, or both, the bending strength of the masonry structure will increase significantly.