Making Row Covers To Protect Plants?

I've recently discovered that something is eating my sunflower plants in one flower bed, and a hibiscus bush/tree on my deck. You mentioned row covers as a deterrent to deer, rabbits, insects, etc staying out of flower beds.

What are row covers? Where can I buy the materials? How do I construct these? Do the row covers only work for plants in the ground? What about a bush/tree that is on the deck?

Thanks and I look forward to hearing from you.

Hardiness Zone: 7b

cp429 from Georgia