Computer network. Devices.
A hub is a network device that is used to connect multiple devices on a single network segment and sends the received data/signals to all devices connected to it. A hub can also function as a repeater. A repeater extends the reach of a network because it rebuilds the signal, which overcomes the effects of data degradation over distance. The hub can also connect to another networking device, like a switch or router that connects to other sections of the network.
Bridge connects two LAN segments and filters network traffic between LAN segments. Bridges keep a record of all the devices on each segment to which the bridge is connected. The bridge also helps to improve the flow of data by keeping frames confined to only the segment to which the frame belongs.
A switch 
dis
a network device that is used to connect multiple devices on a single
network segment to send received data/signals to the device for which
this data is intended using the MAC address.
A modem is an
electronic device that connects to the Internet via an ISP (Internet
Service Provider). The modem converts
digital data to analog signals for transmission over a phone line.
Routers 
connect networks to each other. Routers use IP addresses to forward
packets to other networks. A router can be a computer with special
network software installed or a device built by network equipment
manufacturers.
Wireless access
point provide network access to wireless devices, such as laptops
and tablets. The wireless access
point uses radio waves to communicate with the wireless NIC in the
devices and other wireless access points. An access point has a
limited range of coverage.
Firewall. Hardware firewalls, such as integrated routers, protect data and equipment on a network from unauthorized access. A hardware firewall is a free-standing unit that resides between two or more networks. It does not use the resources of the computers it is protecting, so there is no impact on processing performance.
A firewall should be used in addition to security software. A firewall resides between two or more networks and controls the traffic between them as well as helps prevent unauthorized access. Firewalls use various techniques for determining what is permitted or denied access to a network segment.