Turtles and tortoises are among the slowpokes of the animal kingdom. Their protective shells are a natural armor, so they don't have to outrun many predators. 

While their iconic shells are similar between turtles and tortoises, these creatures are not one and the same. All turtles and tortoises — and terrapins, too — belong to the testudine group of animals, according to National Geographic. Animals in the testudine group are characterized by their shells, as well as a pelvic girdle inside their ribcage that is what makes them walk in such a slow, lumbering fashion. 

Although turtles and tortoises share some anatomical features, there are several differences between them as well. But even before we get to the differences between them, you can know that any shelled animal you see in the wild in Illinois is a turtle, because no tortoises live in the state. 

Of the more than 250 turtle species in the world, 17 live in Illinois, according to the Illinois Department of Natural Resources. Some of the most common are red-eared sliders, painted turtles and snapping turtles. Only a handful of the world's 49 tortoise species live in the United States, most in dry, desert climates.

One of the most distinct differences between turtles and tortoises is their habitat. Turtles are aquatics creatures, and they spend most of their time in water, according to the San Diego Zoo. Tortoises, though, are land-dwelling animals. You may sometimes see turtles on land, where they lay their eggs, or sunning themselves near water on a sunny day, but tortoises are most always seen on land. 

This difference in habitat also creates some physical differences between these shelled creatures. Because they live on land, tortoises have elephant-like legs and feet that help them walk across the terrain, and they have strong forelegs that they use for digging. On the other hand, most turtles have webbed feet that help them swim and move in water, the San Diego Zoo reports.

Their shells are also different. Tortoise shells are usually rounded and dome-shaped, while turtles have flatter, more streamlined shells that help them swim more efficiently, according to the Nashville Zoo. 

While turtles and tortoises have distinct differences, terrapins are another related animal that are somewhat of a middle ground between the two. Terrapins are similar to both turtles and tortoises. Technically, a terrapin is a turtle, but it's not a tortoise, National Geographic reports. 

Terrapin is the technical name for all aquatic and semi-aquatic turtles, so all turtles are terrapins, IDNR reports. Tortoises are not included in this group because they are not aquatic or semi-aquatic.

More specifically, though, true terrapins spend less time in the water than turtles. Terrapins spend about half their time on land and half in the water, according to the National Marine Life Center. They also live near brackish water, which is swampy water that is a mix of fresh and salt water.