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.
IPS (In-Plane Switching) is a technology used for LCDs. It was designed to overcome the main limitations of normal TFTs TN-matrices: relatively slow response times, small viewing angles and low quality color reproduction.
More memory slots (also known as DIMM slots) allow you to add more RAM to your computer. It is also useful when upgrading, as you can add RAM to an empty slot instead of replacing an existing memory module.