IKEA BJÄRSEN shower curtain: rinse and wipe, don't machine-wash
IKEA's BJÄRSEN shower curtain is made from PEVA. The maker says do not machine-wash, bleach, tumble dry, iron or dry-clean; periodically rinse and wipe with a damp sponge.
Shower curtains do not all have the same cleaning instructions. IKEA Korea's BJÄRSEN product page specifies no laundering and advises regular rinsing plus a damp sponge. Other textile curtains may be washable, so identify the exact product and material before cleaning.