Routing tables are not specific to Windows and are more often manipulated by network engineers on other systems, so you may get more information if you just google "static routing tables".
The basic idea is quite simple: when a packet appears, the system checks the table to know which network connection to use to send/foward the packet. Each table entry have 3 key parameters: the prefix (or network address + network mask), the next hop/interface and the metric. The packet's destination address is matched against the prefixes in the table and the longest prefix that matches wins (longest prefix matching) and the packet is send to the corresponding next hop (router ip address) or interface. Metrics are used to resolve ties.
Windows provides two flavours of routing table manipulation commands
netsh. The latter is more powerful, but maybe to difficult to beginners.
route /? will give you some simple help on the former.