The two starting points are what is a default gateway (the address your router presents to every device on your LAN) and RFC 1918 (the 1996 IETF document that reserved 192.168.x.x and the other private address ranges every home router uses). Read those two and the rest of the site becomes a lot less mysterious.
Learn Networking
Understanding networking fundamentals makes every other task on this site easier. When you know what a default gateway actually does, configuring a static IP or troubleshooting a connection failure stops being guesswork. These articles explain the concepts behind the practical guides.