So, this year I plan to harvest my own seeds from my garden, so I am making sure all my seeds are "open-pollinated", which means that they were not pollinated under artificially controlled conditions, aka "hybrids". Hybrids are deliberately bred for specific traits, and their future generations will not necessarily carry on those traits...so your have unreliable and unpredictable results your following season. You can assume that if your seed packages are hybrids unless they specifically say "open-pollinated" or "heirloom".
Although I am planning a full garden of lettuce, spinach, onion, garlic, carrots, potatoes, beans, peas and squash, I am going to put a lot of work into my tomatoes. I'm planning on about a dozen varieties and want to do a lot of experimenting with canning sauces and harvesting seeds. I'm also looking forward to learning everything I can about how they grow, and plan to have a porchful of container pots and hanging baskets all along our south-facing wall.