Each button on the toolbar shows a tooltip if the mouse pointer is held over it long enough. Here is a description of each button:
Add - provides a file chooser dialog box which allows you to chose the Ant build file you want to work with. Multiple build files can be added to the tree.
The traditional name for an Ant build file is "build.xml". In addition to the Add button, AntFarm is setup to automatically load any file named "build.xml" into the tree.
In addition, AntFarm contains the option to load "build.xml" files from any project you may manage using the Project Viewer plugin. To activate this feature, check Global Options -> Plugin Options -> Ant Farm -> Load build files from the Project Viewer plugin.
Remove - removes the currently selected build file from the tree. This does not affect the build file itself in any way.
Run - runs the current target that is selected in the tree. If the currently selected item is a project, AntFarm will run the default target for that build file.
Options Menu - has the following options.
Open Build File On Single Click - lets you navigate through files and targets in a sidekicky way.
Prompt for properties - Ask the user to enter property values in a dialog before executing
Auto-Collapse Targets - This seems to have two purposes. First, it collapses all targets after a build. Second, and this is probably a bug, it seems to hide all targets which do not have a description attribute.
Save all before build - saves all dirty files before starting the build.