What's WPS and what it does?[Wi-Fi Protected Setup]
WPS is a wireless networking standard that tries to make connections between a router and wireless devices faster and easier. It works only for wireless networks that have WPA Personal(deprecated) or WPA2 Personal(recommended) security.
Nowadays, modern routers come with this new technology known as WPS or Wi-Fi Protected Setup. Although, WPS makes it easier and faster to connect your devices to your home network, it, somehow, contains some security flaws, that are well-documented on the internet.
Is WPS recommended?NO!
Even though it's enabled by default, you should find a way to disable it because of the Brute Force Vulnerability. Many Wi-Fi access points that support WPS may be affected. Here are some links which may be useful in this context:
Normally, you can't just connect your wireless devices to a wireless network anywhere, unless you know the SSID and the WPA-Key. You have to first of all choose the network you want to connect with, and enter its security key, but with WPS-enabled, it's not the case anymore.
WPS was originally, invented by the Wi-Fi Alliance.
How WPS can affect your network?An attacker withing required range of the wireless access point, may be able to brute force the WPS PIN and retrieve the password for the wireless network, changing the configuration of the access point, or cause a denial of service. [Reference]
You can do so by entering your ADSL Modem through its IP (usually 192.168.1.1), and disabling WPS on the interface displayed to you.
Further security notes to take: