Regd Business Role - Profile Types

Hi,

I tried to define a new business role. And there I could see some thing called Profile type with the following values:

1. WebClient UI

2. IC Web Client

3. On Demand Business Role

I understand the significance of the first two. However, I don't understand the significance of the third one :  On Demand Business Role.

Could you please help me out, when we use this Profile Type..

Thanks for the needful.

Thanks,

Sandeep