Complex sentence: Hot melt adhesive (or hot glue) is a form of thermoplastic adhesive that is commonly supplied in solid cylindrical sticks of various diameters, designed to be melted in an electric "hot glue gun".
Split into simpler sentences: Hot melt adhesive (or hot glue) is a form of thermoplastic adhesive that is commonly supplied in solid sticks designed to be melted in a special gun. The glue comes in cylinders of various lengths, and is pushed into an electric "hot glue gun".