More USB 3.0 ports allow you to connect more devices to your computer that support USB 3.0. USB 3.0 is an improved version of USB 2.0 which offers faster transfer rates.
Flash-based storage devices such as SSDs have no mechanical components. Due to this they are typically faster, run silently, and are more shock resistant than traditional HDDs.
Apple MacBook Pro (2015) 13" Intel Core i5 2.7Ghz / 16GB / 256GB
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.
Apple MacBook Pro (2015) 13" Intel Core i5 2.7Ghz / 16GB / 256GB
RJ-45 ports are used for LAN (Local Area Network) connections. With more ports you can achieve increased bandwidth across a LAN, or connect to multiple networks. It also has the added benefit of not losing connection to the network if one fails.
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.
Apple MacBook Pro (2015) 13" Intel Core i5 2.7Ghz / 16GB / 256GB