What are they?
Crustaceans!
There are terrestrial, freshwater and marine isopods. They cover almost all habitats and the terrestrial ones are the only crustaceans that live on land permanently.
Most people mean terrestrial isopods when referring to “isopods”. I do, too.
Unlike insects they have 14 legs (seven pairs) and their middle body is also segmented in seven parts.
The mothers carry their young (mancae) in brood pouches until they are developed enough to survive on their own.
They need moisture to survive and, like other destruents, eat mostly dead matter like falles leaves, dead insects and so on.
Why are people interested in them?
Many people keep them as a clean up crew for their terrariums to avoid mold and also just as pets to look at.
They are mostly easy to keep and offer a big variety of colours and forms as well as quite a big variety of species.
Everyone has their own reasons to like them (or dislike them).
Of course, there are also people interested in them from a scientific point of view. Who research them, search them, document them.