|The educated gardener is the best gardener.|
Annuals come next. This includes Marigolds, Zinnia, Cosmos, Petunia and Impatiens. These generally grow and go to seed within a season. They will die after the frost zaps them. Many of these throw their seeds around and come back in the spring without any trouble from you which at times makes people think they are perennial. But these are new plants coming. The old ones died with the cold but not before sowing seeds for the next generation. Isn't that nice of them?
The semi-hardy annual refers to those annuals which can sustain cooler temperatures and if planted in a temperate region may be able to be wintered over sometimes with a just a bit of extra protection like a thick covering of dried autumn leaves or evergreen branches. Snapdragons and at times Four o'clocks have been known to make it through some winters when covered well. It's hit and miss with this bunch. Experimenting is the only way to know for certain.
I hope this has eliminated some confusion. I know you won't want to do any gardening if all that Greek makes your head hurt. Oh, yeah, I forgot. It's Latin. Whatever, just go out there and plant something regardless what it may be called. It'll do you some good I just know it.