Answer: If you are growing annuals and vegetables you need to be more concerned about your average frost date, because many of these plants will not tolerate frost. Some vegetables are early season crops such as the cole crops, peas and greens, others are warm season crops such as tomatoes, peppers, squash, beans and melons. In zone 6 you can grow most annuals and vegetables with no special problems.
If you are growing perennials you need to select plants suited to your zone because the zones indicate winter hardiness. For example, a plant rated "hardy to zone 3" would be fine, a plant rated "to zone 6" would be fine or a plant listed as hardy from "zones 3 to 8" would be fine. Whether to use seeds or plants is a personal choice since both can be done successfully for the most part no matter where you live. Perennials are often purchased as plants however because they can take a year or two to reach blooming size when started from seed.
Since you are so new to gardening you might want to look at a basic book or two to help get you started. One I particularly like is "Garening for Dummies" by Michael MacCaskey, ISBN1-56884-644-4 Dummy Press. In it you will find straightforward general information as well as sections on flowers and vegetables.
You might also check with your local County Extension (746-1970) for their suggestions about what does best in your area. They should also be able to help you with running some basic soil tests and interpreting the results. Soil preparation is probably the most important thing you can do to get your garden off to a good start!
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