This little dot identifies an app that has recently been installed or updated, but which you have not yet opened. In the image below, for example, the little blue dot is next to the Dropbox app.
I have automatic updates enabled on my iPhone, which means that the iPhone will automatically download and install new updates as they become available in the App Store. Since I would not otherwise know that an app update has been installed unless I checked the Updates section of the App Store, this is a helpful little benefit. The little blue dot will go away once you have opened the app. After receiving his Bachelor’s and Master’s degrees in Computer Science he spent several years working in IT management for small businesses. However, he now works full time writing content online and creating websites. His main writing topics include iPhones, Microsoft Office, Google Apps, Android, and Photoshop, but he has also written about many other tech topics as well. Read his full bio here.