It brings back memories of SAT tests, but it's a simple analogy that will help you remember that not all real estate is the same.
A condominium (or condo) is a form of ownership, in which you own the interior wall of the structure, but nothing on the outside (not the land, siding, roof, windows, gutters, etc). This form of ownership wasn't formally recognized until 1958 with the "Horizontal Property Act" though some proto-condos are claimed as early as the 1880's in New York.
A townhome is a style of home construction that was invented in the 1600's, in which (historically) multiple families live in the same upright dwelling (2-3 levels typically).
So, a townhome can be a condo or freehold (traditional ownership). A single-family-detached dwelling can be a condo, a storefront can be a condo... Condo has nothing to do with the type of construction.
Despite this, the CVR MLS includes both condos and townhomes in the same category, separate from single-family residences... making them look like an orangutan with their mouth full of apples. Real estate professionals - know your terminology, and use it correctly to avoid misrepresenting properties.
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