In the past few games, the strength of the Pokémon's attack is dependent on either its Physical Attack or Special Attack and their defense against attacks with Physical Defense and Special Defense. The Physical and Special aspects were determined by type. Physical being Normal, Fighting, Flying, Poison, Ground, Rock, Ghost, Bug & Steel and Special being Water, Fire, Grass, Electric, Psychic, Ice, Dragon & Dark. In Diamond & Pearl however...this changes
Physical/Special Split In Diamond & Pearl, the Physical & Special Attacks are not done solely on type. This time, the classification of each attack and what stats it affects on both your Pokémon and the opponent Pokémon, is determined from the attack itself. Now unlike what most people think, this is not determined through the Physical Contact aspect of the attacks created in Ruby & Sapphire. Essentially, if the attack does something physically without being pure element then it counts as a Physical move. With this, a Physical Attack such as ThunderPunch will affect the Physical Defense of the opponent, meaning you have to be really tactical in your battles.
Checking the Classification Previously, there was no actual way to tell if the attacks were Physical or if they were Special, except through the use of Guides and Websites. However with this massive change, now when you check the Pokémon's attack in the Status Screen, it will give you the classification including an icon to help determine this. The icons are as follows: Physical Special Other

This change to the metagame is truely a groundshaking one. Previous sets that were used for most Pokémon are now made completely redundant. Some Pokémon now are going to be used much less due to their previously most used moves now being of a stat that the particular Pokémon is weak with. Other Pokémon, however, are likely to be used much more now with moves previously in their moveset are now utilising the stat that the respective Pokémon. This brings a whole new level to Pokémon Battling! Click the respective links below for the moves of the specific types: