mor·tar Pronunciation Key (môrtr)
n.
Any of various bonding materials used in masonry, surfacing, and plastering, especially a plastic mixture of cement or lime, sand, and water that hardens in place and is used to bind together bricks or stones.
brick Pronunciation Key (brk)
n.
pl. bricks or brick A molded rectangular block of clay baked by the sun or in a kiln until hard and used as a building and paving material.
Hence, the reference to the actual physical store, as opposed to the internet store.