Hieroglyphics is the everyday name for that picture-writing, especially ancient Egyptian writing: the whole set of picture-signs used to stand for words or parts of words. People say 'Can you read Egyptian hieroglyphics?' as if it were the name of the script. Though actually, many careful writers prefer hieroglyphs (countable little signs) or hieroglyphic writing, and some call hieroglyphics a bit loose or old-fashioned. You will still hear hieroglyphics all the time, in schools and on TV. It looks plural, and it usually stays plural: we do not often say 'a hieroglyphic' to mean the whole system. People also stretch it, with a smile, for any writing they cannot read — a doctor's note, a messy blackboard.