A collection of home network diagrams

a cable/dsl router plus a wireless access point on the same network.

A wireless computer can be added to any ethernet network using a wireless access point of the bridge variety.  The cable/dsl router allows all computers on the ethernet network to access the internet.  The access point allows the wireless PC to join the ethernet network.  In this scenario, the wireless PC would get it's IP settings from the router.  It could then talk to any computer on the internet and see the internet through the router.