For every 1 point of physical defense will reduce physical damage received by 1 point. If a target has more physical defense than the amount of damage a physical attack is initially set to give, the target will only receive one point of damage or zero points if blocked. There are skills and buffs that do reduce physical damage received by a percentage, but that is not a function of Physical Defense itself.
Status Buffs/Debuffs and stuff
Brave - Buffs defenses and attack (Both physical and magic) by X, which stays for X turns.
Charged - Allows a character to use an attack that requires charging. If an attack needs charging to work, using the attack will instead cast Charged onto the person.
Focus - If Focus is in play, and it has X power, then a Confuse attack of lower power cannot be inflicted. If the power of the Confuse is equal to the Focus, then they will cancel each other out.
Steady - Will lower chances for Topple to be inflicted. Increased defenses slightly, but also decreases evade, and accuracy a little.
Inspired - If HP is over half, then an Inspired character can survive from being killed by an attack with 1 HP.
Regenerate - When cast, it will heal a character for (x) health, over the course of X turns.
Defend - Defenses will be increased greatly for a duration of X turns.
Auto-Revive - A halo will appear over the character. If the player is killed in X turns, they will automatically be revived with (x%) health.
Burn - Inflicted by Fire-type attacks. Burns the opponent, dealing them (x) fire damage for X turns. Will not work if enemy is Wet, and will go away if a water attack is used on the enemy. Duration will increase if Tangle is in effect. Will cancel out if Freeze is in effect.
Freeze - Inflicted by Ice-type attacks. The opponent will be encased in ice, and will be unable to attack for X turns. Damaging the enemy when Freeze is in effect will increase damage dealt. Opponent can be unfrozen if hit or healed. The chance for Freeze becomes more likely if enemy is Wet. Will be weakened slightly by Tangle.
Wet - Inflicted by water-type attacks. The enemy will become wet. Increases susceptibility to forest-type attacks, lightning-type attacks, and ice-type attacks. Will make Freeze and Stun more likely and more effective. Weakens the effect of fire-type attacks. Will cancel out Burn.
Stun - Inflicted by lightning-type attacks. Enemy is shocked, keeping them for X turns. Damage dealt to stunned enemies is slightly increased. Can be more effective if enemy was wet proceeding the attack.
Bleed - Can be inflicted by some physical-type and steel-type attacks. Creates a cut in the enemy, making them bleed and take damage every turn. Increases the power of Poison.
Case - Can be inflicted by some steel-type attacks. The enemy is covered is tiny steel fragments. Increases susceptibility to lightning type attacks, fire type attacks, and ice type attacks. Attacking when this effect is in play may cause a powerful bleed.
Dusty - Can be inflicted by some earth-type attacks. Lowers accuracy slightly, and lowers evade even less. Gives higher susceptibility to water attacks, nature attacks, and steel attacks. Gives lower susceptibility to lightning attacks, poison attacks, and wind attacks.
Poison - Inflicted by poison-type attacks. Deals x poison damage for x turns. Increased chance of working if Bleed is in effect. Effect decreased by Dusty.
Stagger - Inflicted by bomb-type attacks. Lets whoever caused the Stagger deal a second attack to the enemy, and ensures that said attack will be a Critical hit.
Enraged - Greatly increases physical attack strength, but forces the use of Basic Attack (hit with weapon).
Tangle - Inflicted by nature-type attacks. Will cover the opponent in types of plants, slightly lowering accuracy and evade. Is increased by water-type attacks and Wet. Will go away if fire-type attacks are used, but gives more likeliness of Burn. Decreases susceptibility to lightning-type attacks.
Break - Lowers random stats by an incredibly minuscule amount. Though weak in itself, it allows for Topple to be inflicted, which would not work in most other cases.
Topple - Can only be inflicted if an opponent is suffering Break, unless in special circumstances. Will knock the enemy over, making them unable to attack and greatly lowering evade, making it easy for their opponents to attack. When Topple is inflicted, defense is also lowered by a lot. Can lead to Daze being inflicted. Topples used can also stack onto each other, extending duration. Will last for X turns.
Daze - Can only be inflicted if an opponent is Toppled, unless in special circumstances. It will literally daze an enemy. The Daze will extend the duration of a Topple by a bit, by either 1 or 2 turns. Will make the chance for critical attacks more likely, as well as giving greater susceptibility to other status effects.
Confuse - Will make an enemy confused, lowering all stats by quite a bit, as well as forcing them to use random attacks beyond their control, for X turns.
Tired - Accuracy and Evade is lowered for X turns. Also gives a higher chance of critical attacks being dealt.
Doom - Will kill the character in X turns.
Seal - Takes away ability to use most magic and physical attacks, with some exception.