There are mainly 4 kinds of Network connectivity Devices
The main function of the network interface card is the sending and receiving of signals; the functioning depends upon the Network Address
Network Address are of two types
An Ethernet hub, active hub, network hub, repeater hub, multiport repeater or hub is a device for connecting multiple Ethernet devices together and making them act as a single network segment. It has multiple input/output (I/O) ports, in which a signal introduced at the input of any port appears at the output of every port except the original incoming.
An ethernet switch is a device used to build a network connection between the attached computers (allows computers to talk to each other). It differs from an ethernet hub: While a hub will send incoming data packets to all ports, a switch understands the packets' addressing scheme and will send any data packet only to its destination port, thus limiting the number of collisions (data sent at the same time).
A router is a device that forwards data packets between computer networks, creating an overlay internetwork. A router is connected to two or more data lines from different networks. When a data packet comes in one of the lines, the router reads the address information in the packet to determine its ultimate destination. Then, using information in its routing table or routing policy, it directs the packet to the next network on its journey. Routers perform the "traffic directing" functions on the Internet. A data packet is typically forwarded from one router to another through the networks that constitute the internetwork until it reaches its destination node.