When client  window is mapped on screen -  Window Manager draws some frame decorations around it, such as Titlebar, resize handles, etc. As such decorations take additional space, it is nesseccary to specify  if resulting larger  window should be moved on screen in any particular direction in order to compensate for discrepancy in size. This is determined by Gravity hint.

Usually Gravity is  set by client itself, depending on geometry specified by the user. For example geometry -10+100 will  set gravity to  NorthEast , while +10+100 will  set gravity to  NorthWest . Sometimes this gravity setting requested by application is incorrect though, due to longstanding tradition of misinterpretation of its meaning. In this cases it may be desired to override gravity. AfterStep users can accomplish that using database file, and definig  new  Style for specific application with Gravity attribute  set . For example it is recommended to  set gravity of popular image viewver XV to be  Static , as it tends to move self assuming that it knows everything.

Below are the list of possible gravity values with explanation of its meaning.