So what do a bunch of dead guys have to do with my baseboard?
You don’t need to have columns in your house to use the rules of thumb that the orders of architecture define. They’re useful in many ways: They can tell you where to put moldings on a wall, how big those moldings should be, and how to combine layers of smaller moldings to make bigger moldings with visually pleasing results.
Because the five orders differ in complexity, each is suited to a different type of building. A simple farmhouse should receive a low level of detail, a row house in the city might get midlevel, and an elaborate mansion would command a high level.
But the orders also differ in size: the height-to-width ratio of the column. Simple orders are wider than complex orders. They mimic the masculine form. Complex orders are more slender to mimic the feminine form. This divergent massing also suits them to different building styles.
In the old days, a military building would be built to Doric (masculine) proportions, and a theater would be built to Corinthian (feminine) proportions. Nowadays, the orders also may translate to different architectural styles, such as Craftsman (masculine) and Victorian (feminine). So consider the type and the style of your house when considering which order to base your moldings on.