You send a photo to your friend face to face through your 4G mobile phone. He or she can receive it at once. But actually, the photo has to go to the base station first. The base station then sends it to your friend. When you use 5G, the photo will not go to a base station. It will go directly (直接地) to your friend's mobile phone. Your friend receives the photo much faster. This is D2D technology.