A network device refers to a component that is used to connect computers in a network. The following are some commonly used network devices: 
Repeater: It is a two-port signal regenerator that is used to extend the length of an Ethernet cable. It produces the original bit pattern for the attenuated signal it receives. It works at the physical layer.

Bridge: It connects two or more LANs. It operates at both physical and data link layers to regenerate the input signals and filter the frames respectively. It filters frames on the basis of a table containing MAC addresses of every node and the port number. It checks for the MAC addresses of the source and destination node contained in a frame and decides or forwarding or dropping the frame.  

Hub: It contains several ports for connecting multiple computers to form a small network. A simple hub is also called concentrator. It works at the physical layer of OSI model where it connects several segments of a LAN together or multiple workstations in a single LAN. 

Switch: It connects two network segments as well as various LANs and WANs together

Router: It connects two networks together and ensures routing of data between nodes and networks. A router has a routing table containing source and destination addresses. On receiving a data packet, the router seeks the destination address from the routing table and ensures the best route of data around network. Having data that, it proceeds to forward the data packet to its appropriate destination. It works on the network layer of OSI Model.

Gateway: It connects more than one network that uses different protocols. It mainly works at the network layer. Gateways, also called protocol converters. 

Modem: It is a hardware device used to send and receive data over a transmission medium, usually telephone lines. The first modem was introduced in 1960 by AT&T Corporation of the US. AT&T designed its Dataphone, the first commercial modem, specifically for converting digital computer data to analog signals for transmission across its long distance network. 
Ethernet
Ethernet is a physical and data link layer technology for local area networks (LANs). Robert Metcalfe and David Boggs was the inventor of Ethernet. It is the name of the most commonly used LAN today. A LAN (Local Area Network) is a network of computers that covers a small area like a room, an office, a building or a campus.

Personal Area Network A personal area network (PAN) is the interconnection of information technology devices within the range of an individual person, typically within a range of 10 meters. Personal area networks can be constructed with cables or be wireless. You can use these networks to transfer files including email and calendar appointments, digital photos and music.

HTTP
The Hypertext Transfer Protocol (HTTP) is an application protocol for distributed, collaborative, and hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web. 

SWIFT Programming Language
Swift is a general-purpose, multi-paradigm, compiled programming language developed by Apple Inc. for iOS, macOS, watchOS, tvOS, and Linux.

SQL 
SQL stands for Structured Query Language, SQL lets you access and manipulate databases. It is an ANSI (American National Standards Institute) standard. SQL consists of a data definition language, data manipulation language, and data control language.

Radix or Base
The radix or base is the number of unique digits, including zero, used to represent numbers in a positional numeral system. Following are Radix of some widely used number systems:
Decimal Number System: Radix-10
Binary Number System: Radix-2
Octal Number System: Radix-8
Hexadecimal Number System: Radix-16