its a sort of successor to adobe's pagemaker, its a publishing software that many companies use, the easiest way for me to discribe it, is illustrator, powerpoint and a bit of photoshop combined... its used to make documents, posters and different buissness media such as id cards of letter heads.. its also used for periodical publications, such as news or advertizements that can be printed out such as posters and such. its a very usefull program for buissness or website only designers, as its not cluttered with filters or all those illustrator/photoshop only applications used for drawing or editing photos.

hope that helped a bit