Access point or bridge to connect old iMac to wireless network?

Hi,

I have a Mac running OSX with DSL and a wireless router. Upstairs I have an older iMac for which I can't find a wireless adapter. So I'm thinking I'll use an AP or bridge to connect to my wireless network, and plug the old iMac in using the ethernet port.

After some googling, I THINK what I need is a wireless bridge, but I want to be sure I'm clear on the difference between APs and bridges. My understanding is this:

• A bridge connects a wired device to a wireless network. That sounds like what I want: the wired device being my iMac, connecting to my wireless router's network.
• An AP connects users on a wireless network to a wired network.

So what would happen if I plug the old iMac into the ethernet port of an AP? Would the AP connect the iMac to the wireless router? Or is it the reverse: the AP would give wireless users access to a hypothetical wired network to which the iMac was connected? Does a single iMac with a cable constitute a wired network?

I've seen combo ap/bridge devices on Newegg, and while I'm sure such a device is likely what I need, I am having some trouble grasping the subtlety of the difference between the modes.

Thanks in advance.

Kman