The Apple networking system software was called AppleTalk. Network connectivity was built into every Macintosh right from the beginning. The first available hardware was the Apple LocalTalk cable system.
LocalTalk was connected in a simple daisy chain configuration, whereby a cable went from one Macintosh computer to another; there could be as many machines as required in the chain until it reached the LaserWriter. The cabling plugged into LocalTalk Connectors, which in turn plugged into the printer port on each network device.
The beauty of the LocalTalk system was that it self-managed the termination issues inherent in a daisy chain. Termination is the process by which unwanted signal reflections at the end of a cable are eliminated. The act of connecting or disconnecting the cable was all that was required to switch termination on or off, providing a simple plug and play solution that was part of the Apple philosophy.
LocalTalk was challenged by a do-it-yourself alternative called PhoneNet, from Farallon, utilising ordinary cheap telephone wires which could be easily cut to length and finished off with RJ11 jacks crimped with a simple handheld tool. It did require some knowledge of termination, but the low price and the flexibility of self assembly eventually killed LocalTalk.
It is believed by some that networking actually came about by accident because of the laser printer. With the Apple II, as with the IBM and Macs before the LaserWriter, one computer talked directly to one printer via one cable. When Apple invented the LaserWriter, it was so expensive that it was inconceivable for there to be only one printer per computer. The LaserWriter only became plausible if several Macs could share one printer. Thus networking was built in to every Macintosh so that they could all be instantly laser printer capable. Before long somebody must have said 'You know, if they can talk to the laser printer, they could talk to each other'.
Postscript files were relatively small and even for big jobs, once the sending Mac had offloaded the data, it did not matter if printing took a few minutes to begin. It was not envisaged and was even incomprehensible, at a time when a whole application including data files would fit on a 400k disk, that huge amounts of data would need to be moved between networked Macs and that this would take so long as to be impractical.
The need for speed was met by Ethernet, which gradually replaced LocalTalk and PhoneNet and is built in today as standard on all Macs.
Network friendliness out of the box was a major point of difference between the Macintosh and other computers.