What's the difference between solid masonry and brick veneer?

Solid Brick vs Brick Veneer
There are two ways to build a brick building: solid masonry and brick veneer. Is one better than the other? If so, why?

Solid Masonry
Solid masonry is the good old-fashioned brick construction that was quite common up until the mid-1900s. This is also known as ‘double brick,' ‘solid brick,' or ‘brick and block' construction. This form of masonry construction uses several layers (wythes) of brick with header bricks to hold them together. Some solid masonry walls built before 1900 were over 20" thick! Because the inner wythe can't be seen from the outside it was commonly substituted with concrete or cinder block. Sometimes metal ties were incorporated into solid masonry walls. Unfortunately, older solid walls with these ties didn't use hot-dip or stainless steel ties so most of those original ties have rusted away.

Solid masonry was undeniably a solid way to build. With an 8 inch or greater wall thickness, they were able to support a wide variety of different roof structures. Carpenters often worked together to build the floor joists into the walls at the same time the brick was going up.