Some reseeders are hardy annuals, but not all are.
My understanding is
Hardy annual- lives a year, not damaged by frost
Half hardy annual- lives a tear, damaged by, but can survive light frost
Tender annual- killed by frost
Tender perennial- perennial in frost free zones, grown as an annual in cold zones
Hardy perennial- not damaged by cold winter.
And these categories vary by the zone you live in.
Karen