Wi-Fi is almost everywhere. We have all connected to a network via Wi-Fi so we understand pretty much how it is working. It handles quite high quantities of data and currently the common Wi-Fi standard is 802.11n, which offers throughput of hundreds of megbits/sec. However, since every good thing has a disadvantage, Wi-Fi is very energy consuming so this protocol is not very good for IoT when talking about wearables or anything else in which every consumption is crucial. It works 2.4 GHz or 5GHz and supports up to 50 m.