ROS packages tend to follow a common structure. Here are some of the directories and files you may notice. (include/package_name, msg, src/package_name, scripts, CMakeLists.txt, package.xml) (1) include/package_name: C++ include headers (make sure to export in the CMakeLists.txt) (2) msg/: Folder containing Message (msg) types (3) src/package_name/: Source files, especially Python source that are exported to other packages. (4) srv/: Folder containing Service (srv) types (5) scripts/: executable scripts (6) CMakeLists.txt: CMake build file (see catkin/CMakeLists.txt) (7) package.xml: Package catkin/package.xml (8) CHANGELOG.rst: Many packages will define a changelog which can be automatically injected into binary packaging and into the wiki page for the package