Final answer:
Spiders have 8 legs while insects have 6 legs. Spiders belong to a different class than insects, specifically the class Arachnida. Arachnids have four pairs of legs while insects have three pairs.
Step-by-step explanation:
Spiders have 8 legs, while insects have 6 legs. The main difference between spiders and insects is that spiders are not classified as insects. While both are arthropods, spiders belong to the class Arachnida, while insects belong to the class Insecta. Arachnids, including spiders, have four pairs of legs, while insects have three pairs of legs.