Term which is used today to describe almost every general purpose firewall appliance which can do some kind of application layer filtering.
The term NGFW (Next Generation Firewall) was originally coined by Palo Alto Networks to marked their system differently from simple packet filters which work only on layer 3/4, application layer gateways (secure mail gateway, secure web gateway,...) and also IDS/IPS (intrusion detection/prevention systems). While the original term naturally matched perfectly only systems by Palo Alto Networks it was quickly adopted by other companies and often replaced the previous IDS/IPS or Secure Gateway marketing. This means it is today used to describe a variety of devices with different capabilities but which all can do some kind of application level filtering.
