Q: What exactly is the remote desktop client?

It's for use with this software:

http://www.apple.com/remotedesktop/

Regards.

Mac OS X is made up of many diffrent parts. For instance there is a part so you can print. Another part that lets you share your printer with other computers. One part lets you share files between computers. And then there another part called apple remote desktop client, witch lets you connect to your computer from another local computer.

Printing Sharing, File Sharing, and Apple Remote Desktop client can all be found in: apple menu, system preferences, sharing. In Sharing Apple Remote Desktop Client is labeled "Remote Management". All these sharing options are off be default. (un checked) You have to check Remote Management if you want to be able to remotely access your computer.

When you run Apple Software Update, it's normal to some times see software updates for Apple Remote Desktop Client. Even if your not using Apple Remote Desktop Client, it's ushally a good idea to isntall these udpates. There may be updates that you want or need, that apple software udpate will not offer untill you install all of the offered updates. Plus these updates can improve performance and security on your computer.

Apple Remote Desktop is some what limited, by default it's not going to work over the internet. BUT it is useful if say your upstairs, with one computer, and you want to connect to another computer from downstairs. Typically Apple Remote Desktop is used by orginizations with many computers to provide remote support.

If your looking for a program to connect to your computer from over the internet, I would suggest looking at  logmein. It's very easy to setup and use.