Is there a difference between Arachnids and Arthropods??

Answer 1

Arthropods are the phylum and arachnids are in that phylum

Answer 2

Superphylum Arthropoda

Older (and many current) classification systems use the Phylum Arthropoda as a category for insects, spiders, centipedes, millipedes, crustaceans, and related groups which have a segmented body, paired and jointed appendages, an external skeleton of chitin, and a number of other related characteristics. This diverse assemblage contains more named species than all other types of animals combined.

Many zoologists now believe that the arthropods actually represent several independent lines of evolution from an ancient ancestor. The classification system used here (Margulis and Schwartz 1998) recognizes three distantly related phyla, now grouped into a Superphylum Arthropoda. The superphylum Arthropoda can be divided into three sub-groups called phyla.
Members of the phylum Chelicerata have mouthparts called chelicerae, which are either fang-like or pincer-like in form. The Chelicerata includes arachnids (spiders, mites, scorpions, and their relatives) as well as horseshoe crabs and sea spiders. The phylum Mandibulata includes Hexapoda (Insects) and Myriapods (centipedes, millipedes, and their kin). These animals all have mouthparts called mandibles, which are jaw-like structures that work against one another (although these mandibles have evolved into bizarre and very un-jawlike structures in some groups). The third phylum, Crustacea, includes shrimps, crabs, and various kinds of small to microscopic aquatic animals. These all have two pairs of antennae and go through a distinctive triangle-shaped, one-eyed nauplius larvae during development.