The first thing I want to say about centipedes is that they are not good pets for the beginner.  While valuable members of the ecosystem they are aggressive hunters, cannot be handle except by the less judicious and are venomous.  While none in the USA are life threatening some species even ones available on the pet trade are.  If you do not die they can leave horrible wounds that can weep for up to a year and a half!

Centipedes are terrestrial arthropods.  They belong to the class Chilopoda and subphylum Myriapods (a myriad of legs).  The largest centipedes belong to the group Scolopendra and some species can reach lengths of 13+ inches.  These large centipedes live in a variety of habitats usually in warmer regions.  In the US the larger species live in desert climates.  Even so they are susceptible to rapid water loss and seek out moisture rich areas.  They shy away from light and are active at night.  Centipedes are predators and will eat anything smaller than them.  This includes small lizards, mice etc.

Centipedes do not bite.  They pinch.  The first pair of legs are modified to act as jaw parts and are complete with poison glands.  Centipedes when threatened will rear up their hind side.  This is often hard to distinguish from the actual head.  They will even strike from this end fooling birds and other would be predators so the important parts can escape.

The name "centipede" is Greek for 100 legs.  They only look like 100.  In fact the number is usually 23 pairs.  Centipedes differ from their cousins millipedes in the number of legs/segment.  Centipedes only have on pair per segment while millipedes have 2pr per segment.