Final answer:
Arachnids, including spiders, are not insects. Insects have six legs, compound eyes, and three body regions, while spiders have eight legs, simple eyes called chelicerae, and two body regions.
Step-by-step explanation:
Arachnids, such as spiders, are not insects. One major difference is that insects have six legs, while spiders have eight legs. Additionally, insects have compound eyes, while spiders have multiple simple eyes called chelicerae. Another difference is that insects have three body regions, while spiders only have two.