Xbox Live is an app that allows you to check your xbox live friends list to see who is online and what they are playing. This is a really nice app when you're not sure if you want to get online or not. One quick look at this app you see what finds are online and who is playing what. Also in this app you can check your messages and send messages. You can check yours and people on your friends list achievements, see their gamer card and add people to your friends list.
I use this app when I'm not sure if I want to get online. I check to see who is on and what they are playing without having to fire up my xbox. Also I use this to check my messages and because it's easier to type, I send most of my messages this way. If you play Xbox online much this is a must have app. The app is free but there is a $1.99 upgrade. The upgrade gets rid of the ads and has some added features, like being able to look at a friends, friends list, people who you have recently played with, and send a message to more than one person.