The device has a display with three full subpixels per pixel, resulting in a sharp and crisp picture. Pixels in some displays (like AMOLED) share one subpixel to preserve space. This can result in a less crisp, slightly blurred image.
You can detach the keyboard of your device and use the screen as a tablet. Detaching the keyboard makes the device lighter and gives you the possibility to switch easily between laptop-mode and tablet-mode.
The device has a standard memory slot (such as an SD or micro SD card slot) so that you can either extend the internal storage with affordable memory modules or you can retrieve data, such as photographs, easily from a memory card.
Retina display refers to a high-resolution screen technology developed by Apple. A Retina display has a high pixel density, with more than 300PPI, which makes it impossible to spot pixels from a normal viewing distance (10-12” from the eyes).