While it is your job to know a great deal about your characters, it is seldom necessary to share it all with the reader, and by "seldom," we mean "never." You, an author, are providing a service to the reader: the service of telling a story. When you call somebody to provide you with a service, the IT guy for example, do you want to hear everything he knows about C++ machine language, SSID encoding, and public key encryption before he tells you how to get back online?