As per Nokia
Display and User Interface
High-resolution LCD display
Large touch screen with pen input 640 x 320 -pixel display with 65,536 colors Partial mode display (640 x 48 pixels) for saving power
Adjustable brightness and contrast Touch-screen, pen-based input with stylus and/or finger
On-screen keyboard and virtual dial pad

Wht is Partial Mode Display?

@Vicky

when I use screen saver mode, after about a minute the display switches off and the screen goes blank except for some status information, which does occupy about 15% of the vertical screen (probably about 50 pixels) and is in monochrome. This is probably is the "Partial Display", as it does stretch across the length (640 pixels) of the screen. The status information includes network, time, date, etc.

Ohh Its a Type Of a Screen Saver

Ohh Its a Type Of a Screen Saver

Must put nicely for marketing mah ;)