In its classic British form, parliamentary sovereignty means Parliament's enactments are the highest form of law: courts interpret them, sometimes very strictly, but cannot invalidate them, and no parliament can bind a future one. The check on a sovereign parliament is political — elections — rather than judicial.
The doctrine travelled with the Westminster model, but most of the family has qualified it. Countries with entrenched constitutions — the US, India, Canada, Australia — subordinate their legislatures to a higher law that courts enforce. The UK and New Zealand keep the doctrine, softened by statutory bills of rights that permit judicial declarations but not invalidation.
Canada blends the traditions: the constitution is supreme and courts strike down inconsistent laws, but section 33 of the Charter — the notwithstanding clause — lets legislatures temporarily insist on a law despite certain rights, a deliberate echo of parliamentary sovereignty.