Packets, Protocols and Addresses
A protocol is basically a set of rules that governs how devices communicate, for example language. this means that all computers can communicate if they follow the same protocol, thus allowing resources and data to be shared. However, if computers do not follow the same protocols they cannot communicate. It's a bit like trying to speak English to a Spanish person: they wont' understand what you are talking about.
Packets are used to transfer data between devices. Imagine it like a lorry. In the tractor unit (header) the driver knows where he is going. In the trailer he has his payload, or data. Because there is a limit to the size of the lorry, the load may have to be transported in multiple lorries. In computing, each data packet contains a single unit of binary code as its payload and in the header control information regarding the identity of the recipient, often in the form of an IP or MAC address.
by splitting the message into smaller packets, there can be more than one data transfer occurring at once down one line (though this is a bit slower). If one packet goes missing, however, the device cannot interpret the full message.
A MAC Address is a unique identifying code given to each device on a network, so that it can be recognised and interacted with by other devices. it takes the for of a 12-bit hexadecimal number or a 48-bit binary number. this means that there can be a total of 281474976710656 MAC addresses, so hopefully they won't be repeated. This ensures that the devices will always have a unique address, but can be a bit difficult to remember or recognise (2AB48E33CA74)