GUIText is a ui element for displaying text which is used inside unity3d before unity version 4.6.
GUIText is a ui element for displaying text with specific font, size and color inside an unity3d scene. It has been used before a new ui system has been introduced in version 4.6 of unity.
Unity 4.6 introduced UI, a User Interface system. You may prefer creating user interface elements with Unity UI instead of GUITexts. Read more about how to use UnityGUI in the UI Overview.