Complex sentence: An electric wire ferrule is metal tube crimped over stranded wire to secure it within a screw terminal usually with electrical insulation protecting any exposed portion of the wire not completely inside the screw terminal post.
Split into simpler sentences: An electric wire ferrule is metal tube crimped over stranded wire to secure the strands within a screw terminal. Electrical insulation may be included to protect any exposed portion of the wire not completely inside the screw terminal post.