These files contain ImageJ macros. You open a macro file using 
File->Open and run it using editor's File->Run Macro command (ctrl-R).
You can also open macro files by dragging and dropping them on the
main ImageJ window. You can run a small piece of macro code by selecting
it in the editor and typing ctrl-R. Some of the files (e.g., MacroSet.txt)
contain macro commands that get installed in the editor's "Macros" menu.

Macros contained in a file can also be installed in the Plugins>Macros
submenu using the Plugins>Macros>Install Macros command. The macros
and macro tools in the file named "StartupMacros.txt" are automatically
installed in the Plugins>Macros submenu and in the toolbar when ImageJ
starts up. The "MacroSet.txt" file contains example macros with keyboard
shortcuts. Note that these shortcuts only work when an image window or
the ImageJ window has focus.

The tools folder contains tool macros that are added to ImageJ's
tool bar when you open the macro file.

Information about the ImageJ macro language (including a 54 pGE PDF),
a list of the built in macro functions and many example macros are
available at

     http://imagej.nih.gov/ij/developer
