LCD (liquid crystal Display): This is probably the most popular screen technology since its being used for tvs and most computer monitors. The screen itseif is made of liquid crystals, they also require some panes of glass and a light source. LCD screens produce some of the most realistic colors on a screen. but the downside to it is that it might not offer better constrast ratio (how deep the 'blacks' are and how light the 'brights' are). some terms associated with the LCD screen are;
TFT (Thin Film Transistor): it makes the wiring of the screen more efficient by reducing the electrodes per pixels. TFT LCD screens have improved color reproduction over the standard or conventional LCD screens
IPS (In-plane Switching): It improves upon the TFT LCD screens by offering much wider viewing angles and better reprodution. Its able to achieve this by keeping all the liqiud crystals parallel to the screen. Devices with LCD screen Galaxy SL, iphone 4, 4s, HTC One X.

AMOLED (Active Matrix Organic light Emitting Diodes):
This screen technology is fairly Old. but its just been recently used in high end phones. It consists of thin layer of polymers that light up when zapped with electric current. AMOLED screens dont require backlight. The benefits of losing backlight are apparent. It enables the screen produce blacks so deep the screen pixels can go to sleep (Shut Off). Shutting off can save your battery if u use a phone with amoled display. Use near to black backgrounds and u can further save ur battery. phone with AMOLED screen galaxy s, galaxy s2, nokia c6-01, Nokia c7, nokia n8 etc