The message log is an in-game UI component displayed at the top left corner of the screen. The Log Message scripting function will append text to this log, while the Clear Log function will clear all text from the log. It can be a great way to display events to the player, for example when they receive an item or a status effect gets applied. It can also be a useful debugging method as an alternative to the Print function, for example to check the value of a variable in a script.
You can set a timeout for messages to be automatically cleared from your game's message log by changing the “Message Log Timeout” setting to a non-zero value. This setting is found in the “User Interface” section of the Game Configuration dialog.