how does cmake work

CMakeLists.txt

cmake_minimum_required(VERSION 2.8)
project(chickadee)

set(CMAKE_AUTOMOC ON)
set(CMAKE_INCLUDE_CURRENT_DIR ON)

find_package(Qt5Widgets REQUIRED)
include_directories(${Qt5Widgets_INCLUDES})
add_definitions(${Qt5Widgets_DEFINITIONS})

find_package(Qt5Quick REQUIRED)
include_directories(${Qt5Quick_INCLUDES})
add_definitions(${Qt5Quick_DEFINITIONS})

find_package(PkgConfig)
pkg_check_modules(XMMS2 REQUIRED xmms2-client-cpp glib-2.0)
include_directories(${XMMS2_xmms2-client-cpp_INCLUDEDIR})
include_directories(${XMMS2_glib-2.0_INCLUDEDIR})

set(CMAKE_CXX_FLAGS "${Qt5Quick_EXECUTABLE_COMPILE_FLAGS} ${XMMS2_CFLAGS}")
set(chickadee_SOURCES src/main.cc)

add_executable(chickadee ${chickadee_SOURCES})

target_link_libraries(chickadee ${Qt5Widgets_LIBRARIES} ${Qt5Quick_LIBRARIES})