The 2.4 GHz standard is better at propagating through solid surfaces, giving it the longest signal range. However, the 2.4 GHz band does not support a high number of individual channels and is often congested, with both other Wi-Fi networks and other types of wireless technology, such as Bluetooth. Also, microwave ovens work at frequencies in the 2.4 GHz band. Consequently, with the 2.4 GHz band, there is increased risk of interference, and the maximum achievable data rates are typically lower than with 5 GHz.
The 5 GHz standard is less effective at penetrating solid surfaces and so does not support the maximum ranges achieved with 2.4 GHz standards, but the band supports more individual channels and suffers less from congestion and interference, meaning it supports higher data rates at shorter ranges.