The 2.4GHz frequency is crowded. Not just with neighbors using the same frequency, but also baby monitors, cordless phones, microwave ovens and more. Modern 802.11n and 802.11ac routers offer "dualband", which means they're sending two network signals; one at 2.4GHz, and one at 5GHz, which is far less crowded and offers more channels.
One drawback is that many device makers only go with the 2.4 GHz receiver. This includes all portable gaming consoles, and also a slew of smartphones. To get a speedy connection activate both networks and connect the mobile devices to the 2.4 GHz network, just enabling the 5GHz network for your laptops and desktops.