Paper Type - A4,A4 Color,etc

Hi,

Could someone please tell me the difference between the following papert types and how does it impact during printing?

A4

A4 Color

A4 Extra

A4 Letterhead

A4 Plain

A4 Plus

A4 Small

A4 Sepcial

Note: The height and width all these paper types seems to be same.

Thanks in adavance.

Vj~