Answer:
From 3rd generation on, Pokemon have natures. Natures influence how your Pokemon grows and what Pokeblocks it likes. A Pokeblock will affect your Pokemon's Contest condtion. A Pokeblock that your Pokemon likes will affect it much more than a Pokeblock it feels neutral about; and a Pokeblock it feel neutral about will affect it more than a Pokeblock it dislikes.
Flavors:
Spicy = Cool
Sour = Tough
Dry = Beauty
Bitter = Smart
Sweet = Cute
Individual Natures:
Adamant = Attack+/Special Attack- Spicy+/Dry-
Brave = Attack+/Speed- Spicy+/Sweet-
Lonely = Attack+/Defense- Spicy+/Sour-
Naughty = Attack+/Special Defense- Spicy+/Bitter-
Bold = Defense+/Attack- Sour+/Spicy-
Impish = Defense+/Special Attack- Sour+/Dry-
Lax = Defense+/Special Defense- Sour+/Bitter-
Relaxed = Defense+/Speed- Sour+/Sweet-
Mild = Special Attack+/Defense- Dry+/Sour-
Modest = Special Attack+/Attack- Dry+/Spicy-
Quiet = Special Attack+/Speed- Dry+/Sweet-
Rash = Special Attack+/Special Defense- Dry+/Bitter-
Calm = Special Defense+/Attack- Bitter+/Spicy-
Careful = Special Defense+/Special Attack Bitter+/Dry-
Gentle = Special Defense+/Defense- Bitter+/Sour-
Sassy = Special Defense+/Speed- Bitter+/Sweet-
Hasty = Speed+/Defense- Sweet+/Sour-
Jolly = Speed+/Special Attack- Sweet+/Dry-
Naive = Speed+/Special Defense- Sweet+/Bitter-
Timid = Speed+/Attack- Sweet+/Spicy-
Serious, Quirky, Bashful, and Docile = Neutral Neutral