Hello superspy468,
Let's answer the second question first: Apps allow you to extend the functionality of your TRAKR in new and exciting ways. With Apps you can do things like make a map of the route you've taken and come back the exact same way, or enhance the night vision capabilities of the TRAKR.
How do you make them? Well, there are two ways. The easier way is to use the App BUILDR on the site
http://www.spygear.net/build.php. With the BUILDR, you can get some pretty interesting Apps without knowing how to write code at all.
If you want to make a really custom App though, you'll need to get the code book and App primer from the help section of the website
http://www.spygear.net/help/apps.php, and then plan on doing some practice and testing.
Don't forget, there are many other agents here on the forum that can help you with writing and testing your app. If you get stuck, post here! Hope that helps, and we can't wait to see what you'll create.