“A brownstone is a type of townhouse made of a brown sand stone that was commonly used to build these types of homes. Townhouses can be built of any material many were made of brick. If it is made of brick it is a townhouse but not a brownstone. So brownstones are townhouses but not all townhouses are brownstones.”

https://fontanarchitecture.com/difference-between-brownstone-townhouse-rowhouse/

“If you are wondering what the distinction between a row house and townhouse is, there really isn't much of one—both are attached to their neighbors. The only real difference is that townhouses might not be exactly the same—they can differ in height, stories, and width, whereas row houses are uniformly laid out.”

https://www.landisconstruction.com/blog/row-houses-explained/