It might help to look at it the other way around. Annuals are plants that die after producing seeds (monocarpic) and are capable of completing their life cycle within a single year. Biennials are similar, but require two growing seasons (approximately, the line between annuals and biennials is sometimes a bit fuzzy). There are always exceptions, but pretty much everything else is a perennial. Whether it is capable of surviving the winters where someone lives is a completely separate and unrelated issue.
Many plants are perennials, but can be grown like an annual if a person chooses to. Perhaps that's where some of the confusion comes in.
