What is the difference between a smooth rat terrier and terrier?

There seems to be a misunderstanding in your question. There is no breed called a "smooth rat terrier."

Rat Terriers are a recognized breed, and they come in two coat varieties:

* Smooth Rat Terrier: This is the most common variety, with a short, smooth coat that is easy to groom.

* Rough Rat Terrier: This variety has a wiry, harsh coat that is longer than the smooth coat.

Therefore, "smooth rat terrier" and "rat terrier" are essentially the same thing, with "smooth" referring to the coat type.

The term "terrier" is more general and refers to a group of dog breeds that share certain characteristics, such as:

* Bold and fearless: They are known for their courage and their ability to hunt vermin.

* Compact and muscular: They are typically small to medium-sized dogs with strong legs and a sturdy build.

* Active and energetic: Terriers need plenty of exercise and mental stimulation.

* Independent and stubborn: They can be strong-willed and require consistent training.

Examples of other terrier breeds include:

* Yorkshire Terrier

* Jack Russell Terrier

* Airedale Terrier

* Scottish Terrier

* Cairn Terrier

So, when you refer to a "terrier," you're talking about a broader category of breeds. A "smooth rat terrier" is a specific breed within that category.