Plant-based or vegan: Primarily comes from plant sources. That means things like vegetables, fruits, grains, and beans, but not things like meat, dairy, eggs, and fish. It's worth a moment to stop and think about the fact that nothing is purely vegan. Even vegetables come from the labor of a human animal.
Gluten-free: Most of my food is gluten-free, and all of it is wheat-free.
Whole-food: This refers to how intact the food is relative to the way it occurs in nature. For example, I would consider a sliced-up zucchini as a whole food. Broccoli florets without the stem is pretty close, but it's more of a whole food if you include the stem. Guar gum, xanthan gum, agave nectar, sugar, carrot juice, etc. are not whole foods because your only eating a select part of the food, rather than the whole thing.
Nightshade-free: I generally avoid nightshade vegetables, but I'm not completely strict. The nightshades include tomates, eggplant, peppers, and potatos (but not sweet potatos).