*Basic

A gateway is a piece of networking hardware or software used in telecommunications networks that allows data to flow from one network to another.[1]

**Intermediate

A network gateway provides interoperability between networks and contains devices, such as protocol translators, impedence matchers, rate converters, fault isolators, and signal isolators.[2] A network gateway requires the establishment of mutually acceptable administrative procedures between networks using a gateway.[3] A network gateway connects a home or office intranet to the interent. If an office or home computer wants to load a web page, at least two network gateways are accessed – one to get from the office or home network to the internet and one to get fromt he internet to the computer that serves the web page.[4] A router may perform some of the functions of a gateway but the idea of a gateway is to join dissimilar network systems. A gateway is defined as a network entity that allows a network to interface with another network with different protocols. [5]

***Advanced

An internet-to-orbit gateway connects computers or devices on the internet to computer systems orbiting the Earth, such as satellites.[6] A cloud storage gateway is a network applicance which translates cloud storage to block based storage protocols.[7] An internet-of-things gateway provides a bridge between IoT devices, the cloud, and user equipment such as smartphones.[8]

Sources

[1] Editors. Definiton of a Gateway. Gartner. Gartner.com
[2] [4] Editors. Gateway (telecommunications). Wikipedia. en.wikipedia.org
[3] Editors. Gateway Computer. On Logic. Onlogic.com
[5] Editors. What is the difference between a gateway and a router? Router Switch. Router-switch.com
[6] Editors. Internet-to-orbit gateway and virtual ground station. Science Direct. Sciencedirect.com
[7] Editors. What is cloud storage gateway? Tech Target. Techtarget.com
[8] Editors. Bridge the Gap with IoT Gateways. Thales Group. Thalesgroup.com