It contains the urdf for the differential drive robot, launch files, default rviz configuration, maze world file and the map generated from it.
It contains the send goal script which makes the robot move to the end of the maze and the amcl launch file.
Individual launch files are given in each folder for specific purposes. Example : original_spawn.launch just spawns the bot into an empty world and so on..
IF you want to go to the main purpose, just launch amcl, it will launch gazebo,rviz,map_server and amcl for you. Change the x,y values in the send_goal.py to change end goal to navigation stack.