A wireless access point is something a wireless client connects to (e.g., PC w/ a wireless network adapter).
[wireless access point]<-- wireless -->[wireless client]
A wireless client "bridge" is also a wireless client, but does so on behalf of a wired client (e.g., PC w/ only a wire network adapter).
[wireless access point]<-- wireless -->[wireless client bridge]<-- wire -->[wired device]
When you use enable ICS (Internet Connection Sharing) under Windows w/ your laptop, that's exactly what you're doing. You're letting your PC act as a wireless client bridge by sharing your wireless connection to the wireless router w/ wired devices on its ethernet port.