Mist: It's FUN to discuss Forms in detail. Where's the fun in saying 'it's just a movie, who cares?'
There are 7 Forms (styles) of lightsabre combat. From the filmakers POV this is good because it means that different fights have different 'looks' to keep them interesting. The difference is in how moves and techniques are executed.
1- Basic swordfighting techniques
2- Fencing style.
3- Defensive style.
4- Acrobatic
5- Aggresive.
6- A 'catch-all' mixing 1, 3, 4 and 5
7- Aggresive and unorthodox.
Palpatine uses Form 6.