Want to know why used ExampleTalker::ExampleTalker

edit

I follow the ros tutorial, reached pub,sub and dynamics.

so i saw git sorce codes how to use.

but i dont know using ExampleTalker::ExampleTalker in node_example/src/talker.cpp

because i understand define add_executable(talker src/nodes/talker_node.cpp src/talker.cpp) and install(DIRECTORY include/${PROJECT_NAME}/ DESTINATION ${CATKIN_PACKAGE_INCLUDE_DESTINATION} FILES_MATCHING PATTERN "*.h" ) to use headerfile to use cpp files.

so we can use include project name / talker.. and use project name :: talker.

but in git source code. it used ExampleTalker and use ExampleTalker::ExampleTalker( Handler ~)

please help me why it use ExampleTalker and ExampleTalker twice ...