"A monitoring and analysis tool for wifi networks."
Although not immediately obvious just from the name of this program, the reality is that Aircrack-ng is a WiFi monitoring and analysis tool that works to check the security of the WEP (Wired Equivalent Privacy) and WPA (Wi-Fi Protected Access) connection numbers.
With Aircrack-ng you can capture information packets from a specific network. Aircrack-ng includes diverse tools, like the Airodump for example, a sniffer that is responsible for capturing the packets for monitoring. It can perform a PTW attack, WEP dictionary attack, Fragmentation attack, it has a WPA Migration mode, improved cracking speed and can capture with multiple cards.
When you have captured enough packets, you have to load them into Aircrack-ng and leave it to decipher the key and find out which network they are from. This way you can know if your network is totally protected from others.